Complicated Magnetic Phases and Presence of Exchange Bias in Off-Stoichiometric Mn50Ni25 + xIn25−x Heusler Alloys

The martensitic transformation (MT), magnetic phases, and exchange bias (EB) effect in Mn50Ni25 + xIn25−x (x = 14.5∼18) Heusler alloys have been investigated. The MT and magnetic state can be tuned significantly by modifying the Ni/In ratio, while the Curie temperature (TC) remains almost unchanged. With increase of the Ni/In ratio, the ferromagnetic components in the studied samples decrease continuously, while the antiferromagnetic components increase and it therefore enhances the exchange interaction as well. All of the samples exhibit negative horizontally shifted loops after field-cooled procedure. In addition, the samples with the compositional range of 15 ≤ x ≤ 16 also present the EB effect in zero field-cooled condition. To evaluate the causes of this scenario, EB field and coercive field as a function of temperature and cooling field have been investigated. The experimental results imply that the spin reconfiguration of superspin glass (SSG) clusters and the competition between antiferromagnetic and ferromagnetic interactions can account for the behavior of EB effect.