Magnetic entropy changes in nanogranular Fe:Ni₆₁Cu₃₉

Authors

Steven A. Michalski, University of Nebraska-LincolnFollow
Ralph A. Skomski, University of Nebraska-LincolnFollow
Tathagata Mukherjee, University of Nebraska-LincolnFollow
Xingzhong Li, University of Nebraska-LincolnFollow
Christian Binek, University of Nebraska-LincolnFollow
David J. Sellmyer, University of Nebraska-LincolnFollow

Date of this Version

4-2011

Comments

Published in JOURNAL OF APPLIED PHYSICS 109, 07A936 (2011). DOI: 10.1063/1.3562254 Copyright 2011 American Institute of Physics. Used by permission.

http://jap.aip.org/resource/1/japiau/v109/i7/p07A936_s1?

Abstract

Artificial environment-friendly Gd-free magnetic nanostructures for magnetic cooling are investigated by temperature-dependent magnetic measurements. We consider two-phase nanocomposites where nanoclusters (Fe) are embedded in a Ni₆₁Cu₃₉ matrix. Several composite films are produced by cluster deposition. The average Fe cluster size depends on the deposition conditions and can be tuned by varying the deposition conditions. The quasiequilibrium Curie temperature of the Fe particles is high, but slightly lower than that of bulk Fe due to finite-size effects. Our experiments have focused on ensembles of 7.7 nm Fe clusters in a matrix with a composition close to Ni₆₁Cu₃₉, which has a T_C of 180 K. The materials are magnetically soft, with coercivities of order 16 Oe even at relatively low temperature of 100 K. The entropy changes are modest, –ΔS = 0.05 J/kg K in a field change of 1 T and 0.30 J/kg K in a field change of 7 T at a temperature of 180 K, which should improve if the cluster size is reduced.