Search

Magnetic and magnetocaloric properties of a solid solution of MnNiSi and FeNiGe alloys with nominal composition Mn 0.53 Fe 0.47 NiSi 0.53 Ge 0.47 have been investigated through dc magnetic measurements in ambient as well as in high pressure conditions. The alloy undergoes magneto-structural transition from the paramagnetic hexagonal Ni 2 In type structure to the ferromagnetic orthorhombic TiNiSi-type structure on cooling around 160 K. The alloy shows significant amount of training effect in magnetization when it is thermally cycled through the first order martensitic transition. We observe a colossal magnetocaloric effect (MCE) ( Δ S = −70.1 J/kg-K for H = 0–50 kOe) in ambient condition around the magneto-structural transition ( ∼ 176 K). Application of external hydrostatic pressure results in a significant decrease in the MCE value of the alloy. Reasonably large value of refrigeration capacity (RC) in ambient as well as in high pressure conditions (RC = 184.4 and 123 J/kg in ambient and 5 kbar of external pressure respectively) confirms its acceptance as a good magnetic refrigerant for practical uses. Metamagnetic behavior of the alloy around the magneto-structural transition presumably plays the key role towards the observation of such colossal value of MCE. [ABSTRACT FROM AUTHOR]

• Structural and magnetic properties of skyrmionic system, Cu 2 OSeO 3 are investigated. • Thermal hysteresis between FC and FCH data is observed. • Lattice distortion at the magnetic transition is noticed. • Large MCE is found near the ferrimagnetic transition for a small change in magnetic field. • The observed anomalous change in Cu(1)-Cu(2) distances tune the strength of the magnetic exchange interactions. [Display omitted] We report here the detailed investigation on structural and magnetic behavior of the polycrystalline sample of Cu 2 OSeO 3. The Mott insulator Cu 2 OSeO 3 is a fascinating material showing skyrmionic state and magneto-electric coupling. We observe clear signature of thermal hysteresis between field-cooled and field-cooled heating data in the low-field magnetization versus temperature curve just below the magnetic ordering temperature of T C ~ 60 K. Temperature dependent powder x-ray diffraction data indicate the presence of lattice anomaly below T C. The sample also shows reasonable value of conventional magnetocaloric effect for small value of applied magnetic field, which can be related to the change in the magnetic structure with field. [ABSTRACT FROM AUTHOR]

Systematic investigations on Ag-doped MnNiGe alloys of nominal compositions MnNi 1 − x Ag x Ge (x = 0.10, 0.15 and 0.20) have been performed through dc magnetic measurements in ambient as well as in high pressure conditions. All the Ag-doped alloys undergo martensitic type structural phase transition with a monotonic decrease in transition temperature with increasing Ag concentration. Room temperature x-ray powder diffraction data confirm the presence of both hexagonal and orthorhombic phase for 10% Ag-doped alloy whereas, 15% and 20% Ag-doped alloys are found to be purely hexagonal in nature. Gradual incorporation of ferromagnetic interaction with increasing Ag-concentration in otherwise antiferromagnetic alloy is clear from the magnetic investigations. Application of external hydrostatic pressure further favors ferromagnetism. In addition, these Ag-doped alloys also show a reasonably high magnetocaloric effect around the magnetic and structural transition temperatures which makes these alloys important for magnetic cooling applications. The robustness of the observed magnetocaloric properties have also been checked by high pressure measurements. • Non-magnetic Ag has been doped in the Mn site of MnNiGe alloy. • The studied alloys undergo first order magneto-structural transition. • Ag-doping induces ferromagnetism in otherwise antiferromagnetic alloys. • The sample shows a large magneto-caloric effect. • Effect of external hydrostatic pressure on the magnetic properties is studied. [ABSTRACT FROM AUTHOR]