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The structure, magnetic transition and magnetocaloric properties in the ternary gallium intermetallic compounds of Ho 2 Ni 2 Ga and Tm 2 Ni 2 Ga have been systematically investigated by using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and magnetization measurements. As found from powder XRD and Rietveld refinement, Ho 2 Ni 2 Ga and Tm 2 Ni 2 Ga crystallized in an orthorhombic structure of the W 2 B 2 Co type belonging to the Immm space group. Both compounds are ordering antiferromagnetically at low temperatures and under low magnetic fields together with a field-induced metamagnetic transition from antiferromagnetic (AFM) to ferromagnetic (FM). Peculiar and similar magnetocaloric properties are observed for both compounds, i. e., an inverse magnetocaloric effect (positive magnetic entropy change, Δ S M ) under low magnetic field changes (Δ H ) and at low temperatures together with a large normal reversible magnetocaloric effect under high Δ H . The positive Δ S M below/at the Néel temperatures ( T N ) is ascribed to first order transition from antiferromagnetic (AFM) to ferromagnetic (FM) states, whereas the negative Δ S M above T N is due to the fact of the magnetic transition from paramagnetic (PM) to ferromagnetic (FM) states. Based on the field-dependent magnetization data, the maximum magnetic entropy change (−Δ S M max ), relative cooling power ( RCP ) and refrigerant capacity ( RC ) are established, and the corresponding values are 9.6 J/kg K, 276 J/kg and 206 J/kg for Ho 2 Ni 2 Ga, and are 4.3 J/kg K, 60 J/kg and 46 J/kg for Tm 2 Ni 2 Ga, respectively, for a magnetic field change of 0–70 kOe. [ABSTRACT FROM AUTHOR]

Two single-phased aluminide RE NiAl 2 ( RE = Ho and Er) compounds have been synthesized by an arc-melting method. The magnetic properties and magnetocaloric effect (MCE) of HoNiAl 2 and ErNiAl 2 have been studied by magnetization measurements. A second-order paramagnetic (PM) to ferromagnetic (FM) phase transition together with a considerable reversible MCE were observed around the Curie temperature T C ∼7.5 K and 5.0 K for HoNiAl 2 and ErNiAl 2 , respectively. Under the magnetic field change (Δ H ) of 0–5 T, the maximal values of magnetic entropy change, refrigerant capacity and relative cooling power are 14.0 J/kg K, 171 J/kg, 213 J/kg for HoNiAl 2 and 21.2 J/kg K, 267 J/kg, 357 J/kg for ErNiAl 2 , respectively. [ABSTRACT FROM AUTHOR]

In this paper, we reported on the magnetic properties and magneto-caloric effect (MCE) of the aluminium compounds Dy 2 CuAl 3 and Tm 2 CuAl 3 based on the magnetization and isothermal magnetization of various temperature measurements. Both compounds obey magnetic phase transition from a paramagnetic (PM) to ferromagnetic (FM) state (second order) around the Curie temperatures of T C  ∼ 24.5 and 4.7 K together with a considerable reversible MCE for Dy 2 CuAl 3 and Tm 2 CuAl 3 , respectively. The magnetic entropy change (-Δ S M ) and the relative cooling power ( RCP ) were estimated and discussed in terms of MCE. Maximum values of -Δ S M are 6.68 and 11.33 J/kg K for Dy 2 CuAl 3 and Tm 2 CuAl 3 , respectively, for a change in field of 0–5 T. Correspondingly, the values of RCP are 364 J/kg and 216 J/kg. [ABSTRACT FROM AUTHOR]