High temperature superconducting (HTS) coils of different shapes (typically circular or trapezoidal) wound on iron or ironless core are fundamental components of many superconducting electrical power devices. A 150-turn (75 turns/pancake) trapezoidal coil in double pancake configuration has been designed and realized in our laboratory of ENEA Frascati. Various epoxy resins and YBCO tapes have been tested in the temperature range room to liquid nitrogen, leading us to the choice of AmSC (American Superconductor) tape for the winding and araldite resin for the impregnation process. The trapezoidal shape has been chosen because of its suitable geometry for practical applications, the results being complementary to what was previously achieved on round shaped HTS coils. The <i>AC</i> transport current losses have been measured using a compensated electrical method and expressed in terms of a linearly frequency dependent resistance. A linear dependence of the losses resistance from frequency was expected and found in agreement with previous results. The current-voltage curve has been measured in zero externally applied field condition, the results being in good agreement with a numerical simulation. The magnetic field distributions, at different air gaps from coil top and zero externally applied filed condition, have been simulated and reported as well.

G. Messina

L. Morici

U. Besi Vetrella

G. Celentano

M. Marchetti

R. Viola

P. Sabatino

<i>AC</i> Loss Measurements of a Trapezoidal Shaped HTS Coil Using an Electrical Method

Charge and spin currents along the <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.16258pt" id="M2" height="6.23217pt" version="1.1" viewBox="0 -6.06959 5.50057 6.23217" width="5.50057pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-100" d="M383 397C383 424 344 448 299 448C244 448 172 409 132 375C66 319 23 227 23 146C23 42 74 -12 146 -12C208 -12 298 30 359 103L343 124C315 95 248 48 192 48C145 48 111 85 111 163C111 228 129 294 151 330C171 363 201 401 241 401C275 401 302 384 325 356C332 347 339 344 348 348C373 360 383 381 383 397Z"/></g></svg>-axis in ferromagnet-insulator-superconductor (F/I/S) tunneling junctions have been studied within the framework of the tunneling Hamiltonian model. As a superconductor <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.2167702pt" id="M3" height="9.23987pt" version="1.1" viewBox="0 -9.0231 6.39475 9.23987" width="6.39475pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-84" d="M449 634C442 637 425 643 405 650C376 660 341 666 307 666C181 666 98 590 98 485C98 400 170 343 215 310L246 288C307 243 343 204 343 147C343 67 291 18 219 18C104 18 61 124 51 202L23 199C28 124 27 71 27 47C47 22 122 -16 204 -16C324 -16 428 60 428 174C428 256 379 309 307 360L276 382C223 419 179 455 179 516C179 576 221 632 293 632C379 632 410 564 418 487L448 490C446 536 446 592 449 634Z"/></g></svg>, HgBa<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>8+<i>δ</i></sub> (Hg-1223) with <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.1625805pt" id="M4" height="9.80889pt" version="1.1" viewBox="0 -9.64631 38.6237 9.80889" width="38.6237pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-226" d="M494 514C482 587 419 712 303 712C238 712 174 667 174 603C174 561 205 514 249 449C219 438 187 422 162 407C93 366 23 283 23 177C23 69 87 -12 190 -12C244 -12 288 5 328 33C406 87 444 170 444 249C444 329 404 391 331 475C265 550 222 605 222 627C222 647 238 657 267 657C355 657 421 585 484 499L494 514ZM359 234C359 143 319 30 219 30C172 30 114 75 114 178C114 275 163 343 195 378C212 397 241 415 269 425C305 382 359 313 359 234Z"/></g><g transform="matrix(.0135,0,0,-0.0135,10.791,0)"><path id="g117-34" d="M535 323V373H52V323H535ZM535 138V188H52V138H535Z"/></g><g transform="matrix(.0135,0,0,-0.0135,22.528,0)"><path id="g113-49" d="M241 635C89 635 35 457 35 312C35 153 89 -12 240 -12C390 -12 443 166 443 312C443 466 390 635 241 635ZM238 602C329 602 354 454 354 312C354 172 330 22 240 22C152 22 124 173 124 313S148 602 238 602Z"/></g><g transform="matrix(.0135,0,0,-0.0135,29.032,0)"><path id="g113-47" d="M113 -12C146 -12 170 11 170 46C170 78 146 103 114 103S58 78 58 46C58 11 82 -12 113 -12Z"/></g><g transform="matrix(.0135,0,0,-0.0135,32.121,0)"><path id="g113-53" d="M456 178V225H360V632H320C217 496 115 347 20 206V178H280V106C280 40 276 34 189 27V0H445V27C364 34 360 39 360 106V178H456ZM280 225H82C149 335 214 431 278 520H280V225Z"/></g></svg> copper-oxide high-<svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.37757pt" id="M5" height="12.5226pt" version="1.1" viewBox="0 -9.14503 11.3764 12.5226" width="11.3764pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-85"/></g><g transform="matrix(.0095,0,0,-0.0095,7.479,3.264)"><use xlink:href="#g50-100"/></g></svg>  superconductor has been selected, and as a ferromagnet <i>F</i>, Fe metal with bcc structure has been selected for simplicity. The electronic structures of above materials have been calculated on the basis of the band theory using the spin-polarized self-consistent-field data for the atomic orbital energies and the universal tight-binding parameters (UTBP) for the interactions. For the <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-4.819109pt" id="M6" height="10.8887pt" version="1.1" viewBox="0 -6.06959 11.3046 10.8887" width="11.3046pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-229" d="M471 401C471 442 455 448 440 448C421 448 389 439 366 424C314 390 233 331 165 242H163L187 345C193 372 197 393 197 409C197 435 189 448 174 448C146 448 80 408 23 349L40 327C64 351 97 373 107 373C115 373 118 366 111 337L29 -4L36 -12C56 -4 83 3 110 9C123 69 136 126 150 172C227 283 336 381 377 381C392 381 396 370 379 298L326 74C290 -77 273 -172 273 -197C273 -219 316 -261 346 -261L353 -246C348 -227 352 -174 374 -66L457 310C467 352 471 381 471 401Z"/></g><g transform="matrix(.0095,0,0,-0.0095,6.354,3.264)"><path id="g54-153" d="M467 531C377 603 299 672 261 710C223 672 145 603 55 531L73 507L230 603V-164H292V603L449 507L467 531Z"/></g></svg> and <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-5.02768pt" id="M7" height="14.6469pt" version="1.1" viewBox="0 -9.61922 65.2676 14.6469" width="65.2676pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-229"/></g><g transform="matrix(.0095,0,0,-0.0095,6.354,3.264)"><path id="g54-161" d="M467 -7L449 17L292 -79V688H230V-79L73 17L55 -7C145 -79 223 -148 261 -186C299 -148 377 -79 467 -7Z"/></g><g transform="matrix(.0135,0,0,-0.0135,11.821,0)"><path id="g113-41" d="M300 -147C201 -63 143 98 143 270S200 602 300 686L282 710C136 610 70 450 70 271V270C70 89 136 -72 282 -170L300 -147Z"/></g><g transform="matrix(.0135,0,0,-0.0135,16.509,0)"><use xlink:href="#g117-34"/></g><g transform="matrix(.0135,0,0,-0.0135,28.247,0)"><path id="g113-50" d="M384 0V27C293 34 287 42 287 114V635C232 613 172 594 109 583V559L157 557C201 555 205 550 205 499V114C205 42 199 34 109 27V0H384Z"/></g><g transform="matrix(.0135,0,0,-0.0135,37.778,0)"><path id="g117-33" d="M535 230V280H52V230H535Z"/></g><g transform="matrix(.0135,0,0,-0.0135,48.759,0)"><use xlink:href="#g113-229"/></g><g transform="matrix(.0095,0,0,-0.0095,55.113,3.264)"><use xlink:href="#g54-153"/></g><g transform="matrix(.0135,0,0,-0.0135,60.58,0)"><path id="g113-42" d="M275 270C275 450 212 609 64 710L45 686C145 604 203 442 203 270S147 -63 45 -147L64 -170C213 -68 275 89 275 270Z"/></g></svg> defined in the present paper, which are tunneling probabilities of the majority and the minority spin electrons, it is shown that the condition <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-5.027709pt" id="M8" height="11.0973pt" version="1.1" viewBox="0 -6.06959 38.6487 11.0973" width="38.6487pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-229"/></g><g transform="matrix(.0095,0,0,-0.0095,6.354,3.264)"><use xlink:href="#g54-153"/></g><g transform="matrix(.0135,0,0,-0.0135,15.606,0)"><use xlink:href="#g117-34"/></g><g transform="matrix(.0135,0,0,-0.0135,27.344,0)"><use xlink:href="#g113-229"/></g><g transform="matrix(.0095,0,0,-0.0095,33.698,3.264)"><use xlink:href="#g54-161"/></g></svg>  means the standard F/I/S tunneling junction with a nonmagnetic insulating layer, and the condition <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-5.02775pt" id="M9" height="13.2786pt" version="1.1" viewBox="0 -8.25085 38.6785 13.2786" width="38.6785pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-229"/></g><g transform="matrix(.0095,0,0,-0.0095,6.354,3.264)"><use xlink:href="#g54-153"/></g><g transform="matrix(.0135,0,0,-0.0135,23.602,0)"><path id="g117-145" d="M-161 592L-215 609L-427 -83L-372 -100L-161 592Z"/></g><g transform="matrix(.0135,0,0,-0.0135,15.606,0)"><use xlink:href="#g117-34"/></g><g transform="matrix(.0135,0,0,-0.0135,27.374,0)"><use xlink:href="#g113-229"/></g><g transform="matrix(.0095,0,0,-0.0095,33.728,3.264)"><use xlink:href="#g54-161"/></g></svg>means the F/I/S tunneling junction with a magnetic insulating layer showing a detectable magnetization. We have found that the charge current and the differential conductance nearly remain the same as the change of <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-4.819109pt" id="M10" height="10.8887pt" version="1.1" viewBox="0 -6.06959 11.3046 10.8887" width="11.3046pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-229"/></g><g transform="matrix(.0095,0,0,-0.0095,6.354,3.264)"><use xlink:href="#g54-153"/></g></svg>, but the spin current is largely changed due to the change of <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-4.819109pt" id="M11" height="10.8887pt" version="1.1" viewBox="0 -6.06959 11.3046 10.8887" width="11.3046pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-229"/></g><g transform="matrix(.0095,0,0,-0.0095,6.354,3.264)"><use xlink:href="#g54-153"/></g></svg>. As an experimental method to detect the change of the spin current, the validity of an X-ray magnetic circular dichroism (XMCD) has been pointed out.

Michihide Kitamura

Yoshitaka Uchiumi

Akinobu Irie

Charge and Spin Currents in Ferromagnet-Insulator-Superconductor Tunneling Junctions  Using Hg-1223 High-<svg  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.37757pt" height="12.5226pt" version="1.1" viewBox="0 -9.14503 11.3764 12.5226" width="11.3764pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-85" d="M620 675H597C578 656 570 650 541 650H144C112 650 104 653 94 675H72C59 618 42 552 23 493L53 491C71 534 88 564 105 585C124 608 144 615 238 615H290L197 121C182 40 174 34 88 28L82 0H361L367 28C275 34 266 38 281 121L374 615H441C522 615 543 608 553 583C562 560 566 531 565 493L597 494C603 551 612 629 620 675Z" /><glyph.data ascent="3473" descent="-2876" horiz-adv-x="637" vert-adv-y="637" /></g><g transform="matrix(.0095,0,0,-0.0095,7.479,3.264)"><path id="g50-100" d="M387 400C387 425 348 451 303 451C247 451 176 414 132 376C69 322 24 228 24 148C24 43 74 -12 147 -12C211 -12 301 33 363 103L346 128C319 99 249 51 193 51C148 51 112 84 112 165C112 230 130 287 154 330C170 359 199 400 243 400C277 400 304 383 326 354C333 345 343 343 354 348C378 360 387 382 387 400Z" /><glyph.data ascent="3443" descent="-2856" horiz-adv-x="411" vert-adv-y="411" /></g></svg> Superconductor

We investigated the chemical reactivity and percolation characteristics of insulating nanocrystalline YBa<sub>2</sub>ZrO<sub>5.5</sub> prepared by modified combustion route and the YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7−<i>δ</i></sub> superconductor composite system. Structural analysis was done by using X-ray diffraction technique, surface morphology of the samples was studied using scanning electron microscopy, and electrical transport measurements like critical transition temperatures (<svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.37757pt" id="M1" height="12.5226pt" version="1.1" viewBox="0 -9.14503 11.3764 12.5226" width="11.3764pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-85" d="M620 675H597C578 656 570 650 541 650H144C112 650 104 653 94 675H72C59 618 42 552 23 493L53 491C71 534 88 564 105 585C124 608 144 615 238 615H290L197 121C182 40 174 34 88 28L82 0H361L367 28C275 34 266 38 281 121L374 615H441C522 615 543 608 553 583C562 560 566 531 565 493L597 494C603 551 612 629 620 675Z"></path></g><g transform="matrix(.0095,0,0,-0.0095,7.479,3.264)"><path id="g50-100" d="M387 400C387 425 348 451 303 451C247 451 176 414 132 376C69 322 24 228 24 148C24 43 74 -12 147 -12C211 -12 301 33 363 103L346 128C319 99 249 51 193 51C148 51 112 84 112 165C112 230 130 287 154 330C170 359 199 400 243 400C277 400 304 383 326 354C333 345 343 343 354 348C378 360 387 382 387 400Z"></path></g></svg>) and self-field transport critical current (<svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.37758pt" id="M2" height="12.1839pt" version="1.1" viewBox="0 -8.80632 9.14095 12.1839" width="9.14095pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-75" d="M429 650H175L169 622C251 614 259 612 244 532L174 152C163 91 152 37 135 -6C109 -72 67 -101 23 -113L33 -144C45 -143 73 -134 102 -119C186 -76 229 -1 254 133L327 532C341 609 347 613 423 622L429 650Z"></path></g><g transform="matrix(.0095,0,0,-0.0095,5.243,3.264)"><use xlink:href="#g50-100"></use></g></svg>) were done by using standard four-probe technique. It is found that, in YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7−<i>δ</i></sub>-nano-YBa<sub>2</sub>ZrO<sub>5.5</sub> composite system, the superconductor and insulator materials coexist as separate phases without any noticeable chemical reaction even after sintering at high temperatures. Furthermore, percolation threshold and critical exponent are found to be <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.42498pt" id="M3" height="12.2313pt" version="1.1" viewBox="0 -8.80632 46.2019 12.2313" width="46.2019pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-87" d="M697 650H468L461 623L492 619C539 613 547 605 518 546C481 471 367 264 278 116H276C239 278 197 500 186 567C180 604 185 613 226 619L252 623L260 650H24L17 623C78 617 92 613 108 533L216 -11H247C365 200 515 462 560 529C616 612 624 615 689 623L697 650Z"></path></g><g transform="matrix(.0095,0,0,-0.0095,7.641,3.264)"><path id="g50-68" d="M690 629C653 643 577 667 483 667C225 667 24 528 24 292C24 92 174 -17 367 -17C448 -17 534 1 570 10C592 34 642 131 658 174C648 180 639 186 629 192C562 89 499 21 382 21C223 21 130 138 130 298C130 467 255 627 462 627C582 627 643 589 650 462L686 466C689 517 688 580 690 629Z"></path></g><g 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xlink:href="#g117-34"></use></g><g transform="matrix(.0135,0,0,-0.0135,22.812,0)"><path id="g113-51" d="M412 140C382 77 369 73 315 73H129L270 222C362 320 402 379 402 466C402 571 322 635 234 635C177 635 130 609 99 576L42 495L64 475C90 514 133 568 201 568C274 568 318 519 318 435C318 349 255 267 193 193C144 135 87 78 32 23V0H405C417 45 427 89 440 131L412 140Z"></path></g><g transform="matrix(.0135,0,0,-0.0135,29.315,0)"><use xlink:href="#g113-47"></use></g><g transform="matrix(.0135,0,0,-0.0135,32.404,0)"><path id="g113-56" d="M447 623H65C61 580 56 530 47 475H76C100 541 106 550 172 550H388C308 376 196 170 91 -1L98 -12L172 -2C268 204 360 408 455 611L447 623Z"></path></g></svg>. And the analysis of the current flow in the polycrystalline samples reveals weak link behavior in the majority of grain connections.

Pullanhiyodan Puthiyaveedu Rejith

Sukumariamma Vidya

Jijimon Kumpukattu Thomas

Electrical Transport and Lowered Percolation Threshold in YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7&#x2212;<i>&#x3b4;</i></sub>-Nano-YBa<sub>2</sub>ZrO<sub>5.5</sub> Composites

A new McMillan formula is assembled for the High Temperature Superconductors that evidences strong coupling in these materials. The McMillan-Hopfield parameter is calculated in each case, in addition to the Bergmann and Rainer enhancement frequency. The cubic symmetry of the CuO layers and the lattice cohesion and oxygen presence are suggested reasons for the effect.

J. H. Turner

An Analysis of Strong Coupling in the High Tc Superconductors

The existence of space inhomogeneous superconductor insulator state (SISIS) found out earlier in polycrystalline samples of high-
					<svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.42778pt" id="M1" height="12.7657pt" version="1.1" viewBox="-0.0498162 -9.33792 14.5489 12.7657" width="14.5489pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-85" d="M620 675H597C578 656 570 650 541 650H144C112 650 104 653 94 675H72C59 618 42 552 23 493L53 491C71 534 88 564 105 585C124 608 144 615 238 615H290L197 121C182 40 174 34 88 28L82 0H361L367 28C275 34 266 38 281 121L374 615H441C522 615 543 608 553 583C562 560 566 531 565 493L597 494C603 551 612 629 620 675Z"/></g><g transform="matrix(.0095,0,0,-0.0095,7.479,3.264)"><path id="g50-68" d="M690 629C653 643 577 667 483 667C225 667 24 528 24 292C24 92 174 -17 367 -17C448 -17 534 1 570 10C592 34 642 131 658 174C648 180 639 186 629 192C562 89 499 21 382 21C223 21 130 138 130 298C130 467 255 627 462 627C582 627 643 589 650 462L686 466C689 517 688 580 690 629Z"/></g></svg>
					 system <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.42776pt" id="M2" height="12.5481pt" version="1.1" viewBox="-0.0498162 -9.12034 74.2166 12.5481" width="74.2166pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g190-67" d="M372 352C427 368 507 407 507 502C507 548 486 592 451 616C420 638 376 650 301 650H44V622C124 616 128 610 128 527V123C128 40 122 34 36 28V0H257C336 0 402 12 453 40C512 72 548 124 548 191C548 291 471 335 372 350V352ZM213 362V558C213 591 216 602 226 608C235 614 258 618 282 618C377 618 415 558 415 490C415 406 369 362 260 362H213ZM213 328H258C380 328 450 283 450 181C450 76 377 35 296 34C231 34 213 53 213 125V328Z"/></g><g transform="matrix(.0135,0,0,-0.0135,8.089,0)"><path id="g190-98" d="M433 39L423 65C413 59 399 54 387 54C370 54 352 69 352 114V299C352 352 342 392 307 422C285 440 255 449 225 449C168 437 102 399 75 379C56 365 44 353 44 339C44 315 69 296 87 296C101 296 111 303 116 319C124 349 133 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134 179 172 179C198 179 245 158 280 141C324 120 375 98 417 98C466 98 507 129 537 168Z"/></g><g transform="matrix(.0135,0,0,-0.0135,29.944,0)"><path id="g113-52" d="M285 378C315 398 338 416 353 432C373 451 384 474 384 503C384 579 325 635 236 635H235C182 635 136 610 108 579L65 516L85 496C110 533 150 575 205 575C258 575 300 543 300 481C300 407 232 369 141 339L147 310C163 315 188 321 211 321C268 321 338 284 338 192C338 94 288 40 217 40C160 40 119 68 93 91C85 98 77 97 69 91C60 84 47 71 46 58C44 46 48 35 62 22C75 10 116 -12 162 -12C234 -12 424 62 424 224C424 297 373 359 285 376V378Z"/></g><g transform="matrix(.0135,0,0,-0.0135,36.448,0)"><path id="g113-49" d="M241 635C89 635 35 457 35 312C35 153 89 -12 240 -12C390 -12 443 166 443 312C443 466 390 635 241 635ZM238 602C329 602 354 454 354 312C354 172 330 22 240 22C152 22 124 173 124 313S148 602 238 602Z"/></g></svg> K) is confirmed on <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.42776pt" id="M4" height="12.5481pt" version="1.1" viewBox="-0.0498162 -9.12034 74.2166 12.5481" width="74.2166pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g190-67"/></g><g transform="matrix(.0135,0,0,-0.0135,8.089,0)"><use xlink:href="#g190-98"/></g><g transform="matrix(.0095,0,0,-0.0095,14.088,3.264)"><use xlink:href="#g50-49"/></g><g transform="matrix(.0095,0,0,-0.0095,18.707,3.264)"><use xlink:href="#g50-47"/></g><g transform="matrix(.0095,0,0,-0.0095,20.955,3.264)"><use xlink:href="#g50-55"/></g><g transform="matrix(.0135,0,0,-0.0135,26.114,0)"><use xlink:href="#g190-76"/></g><g transform="matrix(.0095,0,0,-0.0095,35.267,3.264)"><use xlink:href="#g50-49"/></g><g transform="matrix(.0095,0,0,-0.0095,39.885,3.264)"><use xlink:href="#g50-47"/></g><g transform="matrix(.0095,0,0,-0.0095,42.133,3.264)"><use xlink:href="#g50-53"/></g><g transform="matrix(.0135,0,0,-0.0135,47.293,0)"><use xlink:href="#g190-67"/></g><g transform="matrix(.0135,0,0,-0.0135,55.15,0)"><use xlink:href="#g190-106"/></g><g transform="matrix(.0135,0,0,-0.0135,58.781,0)"><use xlink:href="#g190-80"/></g><g transform="matrix(.0095,0,0,-0.0095,68.983,3.264)"><use xlink:href="#g50-52"/></g></svg>  single crystal. At <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.04990005pt" id="M5" height="10.5763pt" version="1.1" viewBox="-0.0498162 -10.5264 15.0766 10.5763" width="15.0766pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-85"/></g><g transform="matrix(.0095,0,0,-0.0095,8.635,-5.984)"><path id="g50-43" d="M486 158C486 177 478 202 466 220C413 228 386 236 336 262C386 288 413 297 466 304C478 323 486 347 485 366C470 376 444 381 422 380C389 338 368 319 321 288C323 345 329 372 349 422C339 442 322 461 305 470C289 461 271 442 262 422C281 372 287 345 290 288C243 319 222 338 189 380C167 381 142 376 125 366C125 347 133 322 145 304C198 296 225 288 275 262C225 236 198 227 145 220C133 201 125 177 126 158C141 148 167 143 189 144C222 186 243 205 290 236C288 179 282 152 262 102C272 82 289 63 306 54C322 63 340 82 350 102C330 152 324 179 321 236C368 205 390 186 422 144C444 143 470 148 486 158Z"/></g></svg> (<svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.4278pt" id="M6" height="13.9542pt" version="1.1" viewBox="-0.0498162 -10.5264 94.0347 13.9542" width="94.0347pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-85"/></g><g transform="matrix(.0095,0,0,-0.0095,8.635,-5.984)"><use xlink:href="#g50-43"/></g><g transform="matrix(.0135,0,0,-0.0135,18.734,0)"><path id="g117-91" d="M512 -3V55L134 254V256L512 456V514L75 281V230L512 -3Z"/></g><g transform="matrix(.0135,0,0,-0.0135,30.472,0)"><use xlink:href="#g113-85"/></g><g transform="matrix(.0095,0,0,-0.0095,37.95,3.264)"><use xlink:href="#g50-68"/></g><g transform="matrix(.0135,0,0,-0.0135,44.893,0)"><path id="g113-45" d="M95 130C70 130 46 113 46 88C46 72 54 64 59 64C93 55 121 33 121 -3C121 -41 93 -68 44 -88L55 -117C117 -98 186 -56 186 22C186 91 131 130 95 130Z"/></g><g transform="matrix(.0135,0,0,-0.0135,50.253,0)"><use xlink:href="#g113-85"/></g><g transform="matrix(.0095,0,0,-0.0095,58.888,-5.984)"><use xlink:href="#g50-43"/></g><g transform="matrix(.0135,0,0,-0.0135,68.987,0)"><use xlink:href="#g117-132"/></g><g transform="matrix(.0135,0,0,-0.0135,80.725,0)"><path id="g113-50" d="M384 0V27C293 34 287 42 287 114V635C232 613 172 594 109 583V559L157 557C201 555 205 550 205 499V114C205 42 199 34 109 27V0H384Z"/></g><g transform="matrix(.0135,0,0,-0.0135,87.228,0)"><path id="g113-56" d="M447 623H65C61 580 56 530 47 475H76C100 541 106 550 172 550H388C308 376 196 170 91 -1L98 -12L172 -2C268 204 360 408 455 611L447 623Z"/></g></svg> K) the transition from the homogeneous superconducting state into the SISIS occurs. SISIS is characterized by the appearance of two gaps on the Fermi surface, semi- and superconducting, which are modulated in space in antiphase, the electric transport between superconducting regions being carried out due to Josephson tunneling. Thus the whole sample becomes a multiple Josephson system. Nonlinear <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.2129908pt" id="M7" height="9.21094pt" version="1.1" viewBox="-0.0498162 -8.99795 20.4029 9.21094" width="20.4029pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-74" d="M405 650H141L135 622C222 616 230 610 215 535L133 116C118 41 113 33 29 28L23 0H289L295 28C209 33 205 40 219 116L298 535C312 609 317 616 399 622L405 650Z"/></g><g transform="matrix(.0135,0,0,-0.0135,5.802,0)"><path id="g190-46" d="M300 253H71L57 198H286L300 253Z"/></g><g transform="matrix(.0135,0,0,-0.0135,10.643,0)"><path id="g113-87" d="M697 650H468L461 623L492 619C539 613 547 605 518 546C481 471 367 264 278 116H276C239 278 197 500 186 567C180 604 185 613 226 619L252 623L260 650H24L17 623C78 617 92 613 108 533L216 -11H247C365 200 515 462 560 529C616 612 624 615 689 623L697 650Z"/></g></svg> curves are observed on <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.42776pt" id="M8" height="12.5481pt" version="1.1" viewBox="-0.0498162 -9.12034 74.2166 12.5481" width="74.2166pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g190-67"/></g><g transform="matrix(.0135,0,0,-0.0135,8.089,0)"><use xlink:href="#g190-98"/></g><g transform="matrix(.0095,0,0,-0.0095,14.088,3.264)"><use xlink:href="#g50-49"/></g><g transform="matrix(.0095,0,0,-0.0095,18.707,3.264)"><use xlink:href="#g50-47"/></g><g transform="matrix(.0095,0,0,-0.0095,20.955,3.264)"><use xlink:href="#g50-55"/></g><g transform="matrix(.0135,0,0,-0.0135,26.114,0)"><use xlink:href="#g190-76"/></g><g transform="matrix(.0095,0,0,-0.0095,35.267,3.264)"><use xlink:href="#g50-49"/></g><g transform="matrix(.0095,0,0,-0.0095,39.885,3.264)"><use xlink:href="#g50-47"/></g><g transform="matrix(.0095,0,0,-0.0095,42.133,3.264)"><use xlink:href="#g50-53"/></g><g transform="matrix(.0135,0,0,-0.0135,47.293,0)"><use xlink:href="#g190-67"/></g><g transform="matrix(.0135,0,0,-0.0135,55.15,0)"><use xlink:href="#g190-106"/></g><g transform="matrix(.0135,0,0,-0.0135,58.781,0)"><use xlink:href="#g190-80"/></g><g transform="matrix(.0095,0,0,-0.0095,68.983,3.264)"><use xlink:href="#g50-52"/></g></svg> single crystal at temperatures below <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.04990005pt" id="M9" height="10.5763pt" version="1.1" viewBox="-0.0498162 -10.5264 15.0766 10.5763" width="15.0766pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-85"/></g><g transform="matrix(.0095,0,0,-0.0095,8.635,-5.984)"><use xlink:href="#g50-43"/></g></svg>. Dependence of <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.2129908pt" id="M10" height="9.21094pt" version="1.1" viewBox="-0.0498162 -8.99795 20.4029 9.21094" width="20.4029pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-74"/></g><g transform="matrix(.0135,0,0,-0.0135,5.802,0)"><use xlink:href="#g190-46"/></g><g transform="matrix(.0135,0,0,-0.0135,10.643,0)"><use xlink:href="#g113-87"/></g></svg> curves on temperature and magnetic field, typical to a Josephson system, was found out. Besides, a step-like peculiarity at the values of voltage of the order of one and two superconducting gaps shows up. These peculiarities are suppressed by magnetic field much earlier than critical current. The new data firstly correlate with the model of SISIS and secondly permit for the first time to determining directly the energy gap between homogeneous and stratified superconductor states.

L. N. Zherikhina

A. M. Tskhovrebov

L. A. Klinkova

D. A. Balaev

S. I. Popkov

K. A. Shaikhutdinov

D. A. Velikanov

The Stratified Superconductivity in Ba<sub>0.6</sub>K<sub>0.4</sub>BiO<sub>3</sub> Single Crystal: Direct Measurement of Energy Gap between Homo-, and Inhomogeneous States

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International Journal of Superconductivity