Re-entrant spin glass behaviour and magneto-dielectric effect in insulating Sm2NiMnO6 double perovskite

Abstract

The structure and magneto-dielectric properties of Sm 2 NiMnO 6 double perovskite have been investigated.The pure monoclinic bulk phase of Sm 2 NiMnO 6 is an intrinsic B-site disordered ferromagnet showing a second order magnetic phase transition $157 K, along with a low temperature re-entrant spin glass-like transition ($20 K) due to the inherent coupling of Ni-Mn network with Sm 3+ ion. Moreover, it is an insulator with room temperature dc resistivity $10 8 U cm. Furthermore, the high dielectric permittivity ($10 3 ) coupled with a shift in dielectric maxima towards higher temperature with frequency, analysis of the phenomenological parameters (T m , T B , g, DT relax ), and the validity of non-linear Vogel-Fulcher relation, we define this ferromagnetic insulator as a relaxor-type dielectric material. Importantly, it exhibits a positive intrinsic magneto-dielectric (MD) response $2% at 100 kHz under a low magnetic field of 0.5 T close to 150 K. The intrinsic MD effect indicates a correlation between spin orientations on the two magnetic sublattices (Ni and Mn) and the magneto-dielectric coupling in the ferromagnetic regime. The insulating ferromagnetic behaviour coupled with MD effect make Sm 2 NiMnO 6 an attractive spintronic material.

Magnetic frustration and dielectric relaxation in insulating Nd2NiMnO6 double perovskites

“…A similar trend is observed in Sm 2 NiMnO 6 . 33 The magnetic behaviour was further probed by dc bias measurements at different dc fields (H dc ¼ 0, 9, 36, 45, 63, and 81 Oe) superimposed on ac field H ac ¼ 0.17 Oe (frequency ¼ 420 Hz). This is shown in Figs.…”

Functional properties of Sm2NiMnO6 multiferroic ceramics prepared by spark plasma sintering

“…Ref. [22] also reported a high dielectric permittivity ~ 1000 at T=200-300K in Sm 2 NiMnO 6 ceramics consolidated from powders derived by a Pechini process. In fact, our ceramics, as the largest number of double perovskites, show rather a conductivity relaxation, than a dielectric relaxor-like behavior.…”

“…Recent papers concerning Sm 2 NiMnO 6 ceramics prepared by different methods [21,22], explained the dispersion trend of the real part of permittivity as being assigned to a relaxor-like behavior. Yang et al [21] have obtained a large dielectric constant (of ~4500-5000 for Nd 2 NiMnO 6 and ~1000-1100 for Sm 2 NiMnO 6 prepared by solid state reaction process) and assigned these values to the charge ordering of Ni 2+ and Mn 4+ resulting in the formation of polar regions.…”

“…Lin et al [15] reported that the giant dielectric characteristics are due to the charge ordering of Ni 2+ and Mn 4+ . Consequently, the debate related to the Ni-O-Mn electronic interaction offer to the [18,[20][21][22] and one presents density functional theory (DFT) calculation of the electronic band structure in Sm 2 NiMnO 6 double perovskite [23]. Booth et al [18] reported structural and functional properties of different oxides of R 2 NiMnO 6 type, including the R=Sm system produced by solid state reaction.…”

“…[22], a re-entrant spin glass behavior and magnetodielectric effect with good insulating character was reported, although recent ab-initio calculations indicated a full metallic behavior [23]. Therefore, due to the few and controversial data available in the literature the Sm 2 NiMnO 6 double perovskite oxides system prepared by a new method was chosen to be investigated, in search for room temperature multiferroic character.…”