The physical mechanism of magnetic field controlled magnetocaloric effect and magnetoresistance in bulk PrGa compound

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.

The magnetic properties and magnetocaloric effects in binaryR–T(R= Pr, Gd, Tb, Dy, Ho, Er, Tm;T= Ga, Ni, Co, Cu) intermetallic compounds

“…According to the Curie-Weiss law and the definition of χ, M eff is calculated to be 3.6 µ B from the slope of the linear fitting curve. [33] The MH curve at 5 K (not shown in Fig. 1) has also been measured and it is almost coincided with the MH curve at 11 K in high field range.…”

“…Distribution of magnetic moments in each unit cell and the distribution of atoms connected in form of the hexagon ring in yz crystal plane. [33] @295 K χ 2 =1.458 w Rp =0.0708 R p =0.0585 The solid line at the bottom is the difference between the observed and calculated data. The Bragg positions for the nuclear and magnetic structure are marked as short vertical lines.…”

“…The Bragg positions for the nuclear and magnetic structure are marked as short vertical lines. Only nuclear model is considered in the refinement at 295 K and both nuclear model and magnetic model are considered in the refinement at 4.5 K. [33] High resolution neutron powder diffraction (NDP) experiment was then employed to study the magnetic structure of PrGa compound. The NPD experiments were performed at 295 K and 4.5 K, respectively.…”

“…NPD results at 295 K show that PrGa compound has a pure phase and it crystalizes in a CrB-type orthorhombic structure (space group #63 cmcm). Both the nuclear and the magnetic structure models are involved in the calculation at 4.5 K. The magnetic moments are FM-ordered along crystallographic c axis and the ordered magnetic moment is determined to be 2.6 µ B at 4.5 K. [33] Figure 4 shows the isothermal magnetization curve at 11K and the inset of Fig. 4 shows the temperature dependence of χ −1 up to 300 K, where χ is the magnetic susceptibility.…”

Large magnetocaloric effect of NdGa compound due to successive magnetic transitions

“…33 In addition, interesting magnetic properties, transport properties and MCEs were also found in TmGa and PrGa compounds. [34][35][36][37] In this paper, we investigate the magnetic properties and MCEs of NdGa compound. The correlations between MCE and magnetic transitions will be discussed.…”