Magnetic Nanoparticles: A Subject for Both Fundamental Research and Applications

<table>Schematic picture of the free energy of a single domain particle with uniaxial anisotropy as a function of magnetization direction. <svg height="15.25" id="M54" style="vertical-align:-3.276pt" version="1.1" viewbox="0 0 18.8375 15.25" width="18.8375" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<g transform="matrix(.017,-0,0,-.017,.062,11.112)"><path d="M609 650l-19 -162l-30 -2q2 69 -14 94q-9 18 -28.5 26t-74.5 8h-88q-30 0 -37 -6.5t-12 -36.5l-41 -212h103q48 0 69 5.5t32 19t26 50.5h29l-40 -198h-30q2 58 -11.5 70.5t-85.5 12.5h-99l-30 -167q-17 -87 3 -101q18 -15 111 -15q59 0 89 7t54 27q8 7 15.5 16t16 21.5
l14 20.5t15 23.5t13.5 21.5l29 -10q-52 -129 -71 -163h-500l6 28q66 4 83 17.5t28 73.5l77 409q11 61 -0.5 75.5t-78.5 18.5l10 28h467z" id="x1D438"></path></g>
<g transform="matrix(.012,-0,0,-.012,10.8,15.187)"><path d="M594 511q0 -122 -171 -157l1 -2q158 -33 158 -159q0 -52 -34.5 -95t-90.5 -65q-76 -33 -217 -33h-223l8 28q63 5 79.5 19t26.5 72l83 426q9 48 -2.5 60t-77.5 17l6 28h259q195 0 195 -139zM499 509q0 59 -37 83t-91 24q-36 0 -51 -9q-17 -9 -22 -44l-35 -195h62
q82 0 128 37t46 104zM481 199q0 71 -48 102.5t-121 31.5h-56l-37 -201q-11 -58 7.5 -77t80.5 -19q76 0 125 44.5t49 118.5z" id="x1D435"></path></g>
</svg> is the energy barrier hindering the free rotation of the magnetization and <svg height="12.4375" id="M55" style="vertical-align:-0.1638pt" version="1.1" viewbox="0 0 8.5874996 12.4375" width="8.5874996" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<g transform="matrix(.017,-0,0,-.017,.062,12.162)"><path d="M475 507q0 -83 -20 -172t-56 -167.5t-93.5 -129t-125.5 -50.5q-157 0 -157 227q0 78 21.5 164t59 161t96.5 123.5t126 48.5q79 0 114 -58t35 -147zM391 522q0 155 -81 155q-62 0 -111 -82.5t-73 -200.5h253q12 81 12 128zM373 346h-255q-12 -91 -12 -150q0 -72 20 -123
t63 -51q34 0 64 28.5t52.5 77t39 103t28.5 115.5z" id="x1D703"></path></g>
</svg> is the angle between the magnetization <svg height="11.6125" id="M56" style="vertical-align:-0.0pt" version="1.1" viewbox="0 0 16.174999 11.6125" width="16.174999" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<g transform="matrix(.017,-0,0,-.017,.062,11.55)"><path d="M921 25v-25h-332v25q54 5 71.5 22t17.5 62v496l-252 -605h-27l-252 594v-465q0 -57 20 -79q19 -20 81 -25v-25h-234v25q58 6 75 20q16 15 16 63v469q0 41 -17 55q-16 14 -72 19v25h253l199 -472l201 472h252v-25q-56 -5 -72 -23q-16 -17 -16 -74v-428q0 -58 15 -77
q15 -20 73 -24z" id="x1D40C"></path></g>
</svg> and the easy axis.</table>

Journal of Nanomaterials

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Figure 9

Figure 9: Magnetic Nanoparticles: A Subject for Both Fundamental Research and Applications 