Magnetic Phase Transition and Exchange Bias in hbox {Ni}_{45}hbox {Co}_{5}hbox {Mn}_{35.5}hbox {In}_{14.5} Heusler Alloy

Łukasz Dubiel,Antoni Żywczak,Ireneusz Stefaniuk,Andrzej Wal,Wojciech Maziarz

doi:10.1007/s00723-018-1085-z

Abstract

Magnetic properties and exchange bias of hbox { Ni}_{45}hbox {Co}_{5}hbox {Mn}_{35.5}hbox {In}_{14.5} ribbons were investigated by vibrating sample magnetometry (VSM) and electron magnetic resonance (EMR). Curie temperatures determined by using VSM and EMR methods are equal to 374 K and 377 K, respectively. Additionally, the EMR measurements revealed the existence of a weak ferromagnetic resonance (FMR) line in the paramagnetic region. The upward deviation of the integral intensity from Curie–Weis low below temperature T^* and above T_mathrm{C} confirms the existence of ferromagnetic phase in this temperature region. Below T_mathrm{C}, the integral intensity does not saturate, which can suggest the coexistence of different magnetic phases at low temperature range. Additional confirmation on the coexistence of magnetic phases in the sample are asymmetric hysteresis loops associated with the spontaneous exchange bias effect. The dependence of EMR signal on cyclic repetition of measurement is also discussed.

Highlights

Ni-Mn-In and Co-doped alloys have received much attention in recent years, due to their magnetic and structural properties [1]
This behavior is related to the second-order magnetic phase transition
It is noteworthy that practically, there is no temperature hysteresis in the magnetisation as a function of temperature, i.e., heating and cooling give the same shape of M(T). This is the second confirmation that this is the secondorder phase transition and that alloy does not reveal the martensite phase transition in this range of temperature [15]

Summary

Introduction

Ni-Mn-In and Co-doped alloys have received much attention in recent years, due to their magnetic and structural properties [1]. For some fraction of Co, structural phase transition disappears In these groups of materials the unidirectional anisotropy called exchange bias (EB) [8, 9] was observed. The EB effect has been observed in a multilayer structure, but has been reported for Heusler alloys in a polycrystalline form [8] and ribbon shape [6]. The EB effect is related to the interactions between antifferomagnetic (AFM) and ferromagnetic (FM) layers, while in the bulk samples the EB behavior originates from coexisting AFM and FM areas Reports about such coexistence in alloys type Ni-Mn-X can be found in papers [9, 11].

Experimental

Results and Discussion

Conclusion