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The Scientific World Journal
Volume 2014 (2014), Article ID 762765, 13 pages
http://dx.doi.org/10.1155/2014/762765
Research Article

Phototunable Magnetism in Copper Octacyanomolybdate

Department of Physics, Hokkaido University, Sapporo 060-0810, Japan

Received 15 February 2014; Accepted 10 March 2014; Published 8 May 2014

Academic Editors: J. Carlos Krause and A. V. dos Santos

Copyright © 2014 Jun Ohara and Shoji Yamamoto. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We introduce copper molybdenum cyanides of general formula Cu2[Mo(CN)8nH2O, which can serve as optofunctional magnetic devices. Their ground states generally stay paramagnetic down to temperatures of the K order but exhibit a spontaneous magnetization upon photoirradiation usually below a few tens of K. To interest us still further, such a ferromagnetic stateinduced by blue-laser irradiation is demagnetized step by step through further application of red or near-infrared laser pulses. We solve this intriguing photomagnetism. The ground-state properties are fully revealed by means of a group-theoretical technique. Taking account of experimental observations, we simulate applying pump laser pulses to a likely ground state and successfully reproduce both the magnetization and demagnetization dynamics. We monitor the photorelaxation process through angle-resolved photoemission spectroscopy. Electrons are fully itinerant in any of the photoinduced steady states, forming a striking contrast to the initial equilibrium state of atomic aspect. The fully demagnetized final steady state looks completely different from the initial paramagnetism but bears good analogy to one of the possible ground states available with the Coulomb repulsion on Cu sites suppressed.