Effect of magnetic polarons on the magnetic, magnetocaloric, and magnetoresistance properties of the intermetallic compound HoNiAl

Abstract

The effect of distributed exchange parameters on magnetocaloric refrigeration capacity in amorphous and nanocomposite materials J. Appl. Phys. 111, 07A334 (2012) Particle size dependent hysteresis loss in La0.7Ce0.3Fe11.6Si1.4C0.2 firstorder systems Appl. Phys. Lett. 100, 072403 (2012) Magnetocaloric effect and refrigerant capacity in 0.44, 0.46 The magnetic, magnetocaloric, and magnetoresistive properties of the polycrystalline compound HoNiAl have been studied. The temperature variations of magnetization and heat capacity show that the compound undergoes two magnetic transitions, one at 14 K and the other at 5 K. The former is due to the paramagnetic-ferromagnetic transition, while the latter is attributed to the onset of an antiferromagnetic ordering, as the temperature is lowered. The M-H isotherm obtained at 2 K shows a metamagnetic transition with a critical filed of about 13 kOe. The maximum values of isothermal magnetic entropy change and adiabatic temperature change, for a field change of 50 kOe, are estimated to be 23.6 J / kg K and 8.7 K, respectively. The relative cooling power is found to be about 500 J / kg for a field change of 50 kOe. A large magnetoresistance of about 16%, near the ordering temperature of 14 K, is observed for a field of 50 kOe. The magnetic, magnetocaloric, and magnetoresistance data seem to suggest the presence of magnetic polarons in this compound.

Magnetocaloric and magnetotransport properties ofR2Ni2Sncompounds (R=Ce, Nd, Sm, G

“…There may be a contribution from the complex magnetic structure as well, which causes the thermomagnetic irreversibility. 28,29 In Gd 2 Ni 2 Sn, the thermomagnetic irreversibility is found to be very small, which is due to the weak magnetic anisotropy associated with Gd 3+ ion. Since the domain wall pinning effect is quite prominent in materials with large magnetic anisotropy, negligible thermomagnetic irreversibility seen in Gd 2 Ni 2 Sn implies that at least in this compound, the domain wall pinning is the dominant factor in contributing the thermomagnetic irreversibility.…”

Review on magnetic and related properties of RTX compounds

“…It has been reported that compounds of RNiAl series show µeff. higher than the theoretical value, which may arise due to polarization of 3d moment in Ni, and termed as magnetic polaronic effect, which is also responsible for some unusual magnetic properties in these compounds [195,196]. Most of the compounds of RNiAl series are metamagnetic in nature [195,196,197].…”

“…It has been reported that the polaronic effect increases the resistivity of compound due to strong confinement of conduction electrons. On the application of magnetic field, size of polarons grow, coalesce, which causes the delocalization of conduction electrons and results in large MR [196]. YbNiAl shows logarithmic increase of resistivity by 25 % in the temperature between 100 to 10 K, which indicates heavy fermion behavior in this compound [190].…”

“…This RTAl compounds are known to show good MCE. The large MCE in DyNiAl and HoNiAl was reported to arise from the polarization of 3d band of Ni [195,196]. GdNiGa shows very good MCE value around its ordering temperature [449].…”

“…The application of hydrostatic pressure in this compound prefers a low c/a phase and stabilizes AFM ground state, while the uniaxial pressure along the c-axis leads to a FM order in this compound [37]. Some compounds in RNiAl (R=Dy, Ho) show thermo-magnetic irreversibility in magnetization data at low temperatures [195,196]. Generally the TMI decreases with field and disappears at high fields.…”