Magnetocaloric effect in cubically anisotropic magnets

Abstract

Magnetocaloric response in anisotropic single-crystals with cubic crystal symmetry is studied. As compared to isotropic magnets where only paramagnetic-to-ferromagnetic phase transition occurs at Curie temperature (TC=185 K) and magnetization increases monotonously with increasing field and/or decreasing temperature, the spin reorientation phase transitions may occur at lower temperatures (∼115 K) as the magnetic field gets oriented along one of the cubic anisotropy easy axes and induces nonmonotonic increases in magnetization with increasing field and temperature, leading to a spike-like entropy change (−ΔSM) and positive ΔSM at TC, or move the −ΔSM peak towards higher temperatures. Finally, the power laws of maximum −ΔSM and relative cooling power with the field and the double-shifted loop results evidence that only second-order phase transition occurs and the abnormal magnetization behavior completely comes from the spin order evolution due to energy competition. Therefore, the Maxwell relation is applicable. The results are also suitable for multiple anisotropy or polycrystalline materials with well-defined domains.

Magnetocrystalline anisotropy imprinting of an antiferromagnet on an amorphous ferromagnet in FeRh/CoFeB heterostructures

“…Then, the magnetization hysteresis loop is recorded by isothermal cycling of H between 1.0J SM /gμ B and −1.0J SM / gμ B at constant steps of |0.02J SM /gμ B |, where g is the Landé g-factor and μ B is the Bohr magneton. At each temperature/field value, 10 5 Monte Carlo steps were used to equilibrate the system and then discarded, followed by 10 5 Monte Carlo steps for averaging magnetization quantities 25,26 . Finally, 50 sets of independent initial spin states were chosen to minimize the errors.…”

Prediction of Magnetocaloric Effect Induced by Continuous Modulation of Exchange Interaction: A Monte Carlo Study

“…The relationship between MCE and phase transitions implies the anisotropy and exchange energies responsible for the large MCE besides the external magnetic field, and from the energy-saving point of view, the rotary MCE based on the anisotropy contributing to ∆ S M has been developed and studied for the aim of reducing the cost of external magnetic field energy [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. On the other hand, effective methods to control the magnetocaloric properties and their working temperatures (probably around the magnetic phase transition temperature) such as partial substitution [ 22 , 23 ], application of hydrostatic pressure [ 24 ], and hydrogenation [ 25 ] have been proposed.…”