Rapidly annealed exchange-coupled Sm-Co/Co multilayers

Authors

J. Zhou, University of Nebraska - Lincoln
Ralph Skomski, University of Nebraska-LincolnFollow
Yi Liu, University of Nebraska-LincolnFollow
Yucheng Sui, University of Nebraska-LincolnFollow
W. Liu, University of Nebraska - Lincoln
David J. Sellmyer, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

5-15-2005

Comments

Published by American Institute of Physics. J. Applied Physics 97, 10K304 (2005). ©2005 American Institute of Physics. Permission to use. http://jap.aip.org/jap/.

Abstract

In exchange-coupled two-phase permanent magnets, the length scale of soft phase is limited to about twice of the domain-wall width of the hard phase. To optimize the energy product, it is important to realize this length experimentally. In this work, we investigate the Sm–Co/Co hard/soft multilayers with varying thickness of soft phase layers. On rapidly annealing, the multilayered hard-soft structure forms. Transmission electron microscopy micrography confirms that the multilayer structure is retained after the annealing. Single-phase-like hysteresis loops are obtained for samples with Co layers up to 13 nm thick. This behavior indicates that the soft phase is well exchange coupled to the neighboring SmCo_z hard phase. An optimal energy product of 16.6 MGOe has been obtained. Longer annealing time results in more diffusion at the interface and yields two-phase-like hysteresis behavior. Direct current demagnetization measurement shows exchange-spring behavior of the samples annealed for longer time. Micromagnetic simulations with varying interface exchange coupling have been performed to compare with the experimental results.