Abstract
The structural, magnetic, and magnetotransport properties of Ni50-xCrxMn37In13 Heusler alloys have been synthesized and investigated by x-ray diffraction (XRD), field and pressure dependent magnetization, and electrical resistivity measurements. The partial substitution of Ni by Cr in Ni50Mn37In13 significantly improves the magnetocaloric effect in the vicinity of the martensitic transition (TM). This system also shows a large negative entropy change at the Curie temperature (TC), making it a candidate material for application in a refrigeration cycle that exploits both positive and negative magnetic entropy changes. The refrigeration capacity (RC) values at TM and TC increase significantly by more than 20 % with Cr substitution. The application of hydrostatic pressure increases the temperature stability of the martensitic phase in Ni45Cr5Mn37In13. The influence of Cr substitution on the transport properties of Ni48Cr2Mn37In13 is discussed. An asymmetric magnetoresistance, i.e., a spin-valve-like behavior, has been observed near TM for Ni48Cr2Mn37In13.
Highlights
Magnetic materials with large magnetic entropy changes (∆SM) are potential candidates in new technologies where energy efficiency is a concern, e.g., magnetic refrigeration, spintronics, etc.[1,2] Due to the rapid change in magnetization in the vicinity of the phase transitions, magnetic materials undergoing first order transitions (FOT) exhibit large ∆SM as well as sharp changes in other magnetic characteristics.[3]
The x-ray diffraction (XRD) patterns from the martensitic phases were characterized by a low intensity of about 15-25% than of austenitic phase
For lower Cr concentrations, the X-ray patterns can be related to the modulated martensitic phase 10M and austenitic phase (AP) (see Figure 1(a))
Summary
Magnetic materials with large magnetic entropy changes (∆SM) are potential candidates in new technologies where energy efficiency is a concern, e.g., magnetic refrigeration, spintronics, etc.[1,2] Due to the rapid change in magnetization in the vicinity of the phase transitions, magnetic materials undergoing first order transitions (FOT) exhibit large ∆SM as well as sharp changes in other magnetic characteristics.[3]. In Ni-Mn-In Heusler alloys, magnetostructural transitions and associated magnetic properties have been observed such as giant normal and inverse magnetocaloric effects,[9,10,11,12] giant magnetoresistance,[13] and giant Hall effects.[14] The Heusler alloys Ni–Mn–In provide an excellent opportunity to vary the martensitic transition temperature (TM) and magnetic states of austenitic phase (AP) and martensitic phase (MP) by changing the composition or doping with different 3d elements which strongly influence the magnetic, magnetocaloric, and electrical properties. It has been observed that the substitution of Ni by Co in Ni-Mn-In Heusler alloy strongly affects the magnetic state of the martensitic phase, the magnetic entropy changes, and the electrical properties of the alloys.[15] Recently, large magnetocaloric effects in Co and Cr doped Ni-Mn-In Heusler alloys have been predicted using first principles and Monte Carlo approaches.[16] in order to develop. We report the variation in the crystal structure, magnetocaloric, thermomagnetic, and transport properties of Ni50-xCrxMn37In13 (x=0, 2, and 5) induced by a small amount of Cr introduced into the Ni sites, as well as the effects of hydrostatic pressures (up to 0.778 GPa) on these properties
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