Magnetic Properties of LaCr1−xMxSb3 (M=V, Mn, Fe, Cu, and Al)

The influence of Cr substitution by various metals (M=V, Mn, Fe, Cu and Al) on the magnetic state of the itinerant intermetallics La(Cr,M)Sb3 was studied by magnetization and magnetic susceptibility measurements up to 55 kG at 5 K and from 4.2 to 400 K, in a magnetic field of 1000 G, respectively. It was found that the Curie temperature (TC) and magnetization (M) of these compounds depend nonlinearly on the concentration, remaining in the vicinity of the values of TC and M measured for LaCrSb3. Curie temperatures and magnetization values at 55 kG are suppressed by Mn, Fe, V, and Cu, and have a slight maximum at low Al concentration (about 5%)

The Structural and Magnetic Properties of Ni2Mn1−xMxGa (M = Co, Cu)

In Ni2MnGa (cubic structure of L21 type) a first order martensitic structural transition, from the parent cubic (austenitic) phase to a low temperature complex tetragonal structure, takes place at TM = 202 K, and ferromagnetic order in the austenitic phase sets at TC = 376 K. In this work, the Mn sites in Ni2MnGa have been partially substituted with magnetic Co and nonmagnetic Cu, and the influence of these substitutions on the structural and magnetic properties of Ni2Mn1−xMxGa (M = Co and Cu) have been studied by XRD and magnetization measurements. X-ray diffraction patterns indicate that the Co doped system possess a highly ordered Heusler alloy L21 type structure for 0.05\u3cx\u3c0.12, and the Cu doped compounds possess L21 structure for 0.05\u3cx\u3c0.10. The ferromagnetic ordering temperature increases with increasing Co concentration for this system, and rapidly decreases with increasing Cu concentration. Both systems show the increase in TM with increasing Co and Cu concentration. (T-x) phase diagrams have been plotted. The results are discussed in terms of 3d-electron concentration variation

Exchange Bias Behavior in Ni–Mn–Sb Heusler Alloys

The authors report the observation of exchange bias in bulk polycrystalline Ni50Mn25+xSb25−x Heusler alloys. Shifts in hysteresis loops of up to 248 Oe were observed in the 5 T field cooled samples. The observed exchange bias behavior in Ni50Mn25+xSb25−x is attributed to the coexistence of antiferromagnetic and ferromagnetic exchange interactions in the system. Such behavior is an addition to the multifunctional properties of the Ni50Mn25+xSb25−x Heusler alloy system

Phase Transitions and Corresponding Magnetic Entropy Changes in Ni2Mn0.75Cu0.25−xCoxGa Heusler Alloys

Detailed studies of room temperature crystal structures, phase transitions, and related magnetic entropy changes (ΔSm) in shape memory alloys Ni2Mn0.75Cu0.25−xCoxGa (x = 0.0, 0.01, 0.02,0.025 0.03, 0.05) have been carried out by x-ray diffraction, magnetization, and thermal expansion measurements in magnetic fields of up to 5 T and in a temperature interval of 5–400 K. The high temperature austenitic cubic phase passes through a magnetic transition to ferromagnetic state and a structural transition to martensitic phase at the same temperature for all samples of the Ni2Mn0.75Cu0.25−xCoxGa system. The first order magnetostructural transition temperature increases from 308 to 345 K with increasing Co concentration. All of the alloys in the Ni2Mn0.75Cu0.25−xCoxGa system were found to possess large magnetic entropy changes. The maxima in the magnetic entropy changes ranged from ΔSmmax = −48 J/kg K to −64 J/kg K in a temperature range of 308–345 K

Exchange Bias in Bulk Mn Rich Ni–Mn–Sn Heusler Alloys

An experimental study on the exchange bias properties of bulk polycrystalline Ni50Mn50−xSnx Heusler alloys has been performed. Martensitic transformations have been observed in the alloys for some critical Sn concentrations. The alloys, while in their respective martensitic phases, are found to exhibit exchange bias effect. Shifts in hysteresis loops of up to 225 Oe were observed in the 50 kOe field cooled samples. The observed exchange bias behavior in Ni50Mn50−xSnx is attributed to the coexistence of antiferromagnetic and ferromagnetic exchange interactions in the system

Giant reversible barocaloric response of (MnNiSi)(1-x)(FeCoGe)(x) (x=0.39, 0.40, 0.41)

MnNiSi-based alloys and isostructural systems have traditionally demonstrated impressive magnetocaloric properties near room temperature associated with a highly tunable first-order magnetostructural transition that involves large latent heat. However, these materials are limited by a small field-sensitivity of the transition, preventing significant reversible effects usable for cooling applications. Instead, the concomitant large transition volume changes prompt a high pressure-sensitivity, and therefore, promise substantial barocaloric performances, but they have been sparsely studied in these materials. Here, we study the barocaloric response in a series of composition-related (MnNiSi)1-x(FeCoGe)x (x = 0.39, 0.40, 0.41) alloys that span continuously over a wide temperature range around ambient. We report on giant reversible effects of ~40 J K-1 kg-1 and up to ~4 K upon application of ~2 kbar and find a degradation of the first-order transition properties with pressure that limits the barocaloric effects at high pressures. Our results confirm the potential of this type of alloys for barocaloric applications, where multicaloric and composite possibilities, along with the high density and relatively high thermal conductivity, constructively add to the magnitude of the caloric effects.Peer ReviewedPostprint (published version