Eur. Phys. J. B (2015) 88: 114
https://doi.org/10.1140/epjb/e2015-50868-0

Regular Article

Aging and rejuvenation in a ferromagnetic Ni₃Al

National Institute for Materials Science, 305-0047 Tsukuba, Japan

^a e-mail: MAMIYA.Hiroaki@nims.go.jp

Received: 18 December 2014
Received in final form: 27 February 2015
Published online: 7 May 2015

Abstract

Aging and rejuvenation phenomena, recently observed in ferromagnetic-like phases of complicated magnets, are studied using a simple itinerant-electron ferromagnet, Ni₃Al. Results show that relaxation times of the magnetic response are widely distributed, hence, magnetic domain walls are collectively pinned in a multi-valley structured potential. The absorptive component of the ac-susceptibility gradually decreases with isothermal aging, and hence the domain-wall conformation becomes stabilized in following deeper valleys. If the temperature is shifted slightly after such isothermal aging, the absorptive component temporarily rises as if rejuvenated. This rejuvenation-like phenomenon is always accompanied by acceleration of the magnetic relaxations, regardless of cooling/heating. This thermal perturbation induced de-pinning indicates that the multi-valley structure itself significantly changes with temperature. In other words, the rejuvenation as well as aging can be explained using temperature-sensitive collective pinning of magnetic domain walls. We can hence say that they are intrinsic properties in actual ferromagnets with irregularly distributed pinning centers.