Structural, magnetic, and magnetocaloric properties of R2NiMnO6 (R = Eu, Gd, Tb)

Abstract

The crystal structure, cryogenic magnetic properties, and magnetocaloric performance of double perovskite Eu2NiMnO6 (ENMO), Gd2NiMnO6 (GNMO), and Tb2NiMnO6 (TNMO) ceramic powder samples synthesized by solid-state method have been investigated. X-ray diffraction structural investigation reveal that all compounds crystallize in the monoclinic structure with a P21/n space group. A ferromagnetic to paramagnetic (FM-PM) second-order phase transition occurred in ENMO, GNMO, and TNMO at 143, 130, and 112 K, respectively. Maximum magnetic entropy changes and relative cooling power with a 5 T applied magnetic field are determined to be 3.2, 3.8, 3.5 J/kgK and 150, 182, 176 J/kg for the investigated samples, respectively. The change in structural, magnetic, and magnetocaloric effect attributed to the superexchange mechanism of Ni2+–O–Mn3+ and Ni2+–O–Mn4+. The various atomic sizes of Eu, Gd, and Tb affect the ratio of Mn4+/Mn3+, which is responsible for the considerable change in properties of double perovskite.

Magnetoelastic Coupling and Cryogenic Magnetocaloric Effect in Two-Site Disordered GdSrCoFeO6 Double Perovskite

“…Notably, n deviates from the mean-field ferromagnet value n = 2/3, which could be a consequence of the existence of local inhomogeneities or magnetic domains in the vicinity of the ordering temperature. Similar values have been reported for other DP . The existence of FM/AFM magnetic competition, canted AFM, and long-range ordering of Gd 3+ ions may be a possible reason for such a value of −Δ S M max in GdSrCoFeO 6 . , …”

“…Similar values have been reported for other DP. 107 The existence of FM/AFM magnetic competition, canted AFM, and long-range ordering of Gd 3+ ions may be a possible reason for such a value of −ΔS M max in GdSrCoFeO 6 . 108,109 An interesting point regards the link between the magnetoelastic coupling and the MCE.…”

Magnetocaloric effect and Griffiths phase analysis in a nanocrystalline Ho2NiMnO6 and Ho2CoMnO6 double perovskite

“…4(a and b). Based on the thermodynamic theory, the isothermal eld-induced magnetic entropy change (DS) from 0 to H max can be calculated by using the relation: [12][13][14][15] DSðT; HÞ ¼ S M ðT; HÞ À S M ðT;…”

“…6 depicts -DS Max with respect to the magnetic eld along with power law tting, and the resulting values of "n" are 1.01 and 1.10 for HNMO and HCMO compounds, respectively, which are higher than the reported values (n = 0.67) for mean eld ferromagnetic materials. 12 The magnetic order can be analyzed from the equation DS Max f H n , where the value of n depends on magnetic eld and temperature, which can be calculated as follows: [52][53][54][55] NðT; HÞ ¼ dlnjDSðT; HÞj dlnðHÞ…”

“…5 So far, numerous magnetocaloric materials have been explored for possible applications in magnetic refrigeration (MR) at a wide range of temperatures from ambient to liquid He temperature. The various materials with a substantial MCE at low temperatures, such as rare-earth based alloys, [6][7][8] rare-earth amorphous alloys, 9,10 rare earth oxides, 11,12 and double perovskites [13][14][15][16][17][18] have been extensively investigated over the years. Among them, magnetic oxides are a class of materials that are being explored for their potential applications in magnetic refrigeration technology, due to their high resistivity and low eddy current loss.…”