Abstract
The PrGa compound shows excellent performance on the magnetocaloric effect (MCE) and magnetoresistance (MR). The physical mechanism of MCE and MR in PrGa compound was investigated and elaborated in detail on the basis of magnetic measurement, heat capacity measurement and neutron powder diffraction (NPD) experiment. New types of magnetic structure and magnetic transition are found. The results of the NPD along with the saturation magnetic moment (MS) and magnetic entropy (SM) indicate that the magnetic moments are randomly distributed within the equivalent conical surface in the ferromagnetic (FM) temperature range. PrGa compound undergoes an FM to FM transition and an FM to paramagnetic (PM) transition as temperature increases. The magnetizing process was discussed in detail and the physical mechanism of the magnetic field controlled magnetocaloric effect (MCE) and the magnetoresistance (MR) was studied. The formation of the plateau on MCE curve was explained and MR was calculated in detail on the basis of the magnetic structure and the analysis of the magnetizing process. The experimental results are in excellent agreement with the calculations. Finally, the expression of MR = β(T)X2 and its application conditions were discussed, where X is M(H)/Meff, and Meff is the paramagnetic effective moment.
Highlights
Ever since the discovery of giant magnetoresistance (GMR) in Fe/Cr multilayers[1], much attention has been paid to artificial multilayer systems[2]
Magnetic refrigeration based on magnetocaloric effect (MCE) is different from the conventional refrigeration based on gas compression/expansion
We studied the magnetic structure of PrGa compound by means of magnetic measurement, heat capacity measurement and high-resolution neutron powder diffraction (NPD) experiments
Summary
Ever since the discovery of giant magnetoresistance (GMR) in Fe/Cr multilayers[1], much attention has been paid to artificial multilayer systems[2]. The occurrence of GMR effects in multilayer systems is usually ascribed to the spin-dependent electron scattering both at layer boundaries and within each layer[3,4] In addition to these artificial magnetic multilayers, many other systems such as granular alloys, oxides and bulk intermetallic compounds were found to have significant magnetoresistance (MR) effects. People have done lots of works on studying the magnetic properties, MCE and MR of many materials including R based intermetallic compounds[12,13,14]. The physical mechanism of plateau-type MCE in PrGa compound need to be studied further. The magnetoresistance in granular ferromagnetic system and the doped magnetic semiconductors has been studied[9,10], the magnetic field controlled physical mechanism of MR in bulk materials is still lacking. A physical model was built to describe the mechanism of electron-magnon scattering in PrGa compound
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