Temperature behavior of anhysteretic magnetization in granular magnetic systems

Temperature measurements of the anhysteretic, magnetization M were performed on nearly-superparamagnetic, granular Cu90Co10 submitted to different Joule-heating currents using a VSM. Below about 500 K, the anhysteretic magnetization is fully reversible. All isothermal M(H) curves may be fitted by a superposition of Langevin functions with distributed magnetic moments; however, the reduced magnetization M/M-s is not observed to scale with H/T; on the contrary, all curves are nearly exactly coincident when plotted against M-s/T. This result is phenomenologically interpreted in terms of an apparent average magnetic moment linearly growing with the ratio T/M-s. (C) 2001 Elsevier Science B.V. All rights reserved.