Rare-earth tuned magnetism and magnetocaloric effects in double perovskites R ₂NiMnO₆

Abstract

We present a comprehensive experimental study of magnetization {\color {blue} ($2 < T < 300$~K, $1 < H < 8$~T)} and magnetocaloric effect in double perovskite materials $R_2$NiMnO$_6$ with $R =$ Pr, Nd, Sm, Gd, Tb, and Dy. While a paramagnetic to ferromagnetic transition, with T$_{\rm C}$ in the range $\sim 100 - 200~$K, is a common feature that can be attributed to the ordering of Mn$^{4+}$ and Ni$^{2+}$ magnetic moments, qualitatively distinct behavior depending on the choice of $R$ is observed at low temperatures. These low-temperature anomalies in magnetization are also manifest in the change in magnetic entropy, $-\Delta S_{M}$, whose sign depends on the choice of $R$. In order to understand these results, we present theoretical analysis based on mean-field approximation and Monte Carlo simulations on a minimal spin model. The model correctly captures the key features of the experimental observations.

Giant and highly anisotropic magnetocaloric effects in single crystals of disordered-perovskite RCr0.5Fe0.5O3 (R = Gd, Er)

“…Extensive investigations on the series of compounds based on diverse magnetic phases and interactions reveal intriguing physical properties, such as metamagnetism 25 , 26 , exchange bias 27 , 28 , magnetodielectric effect 22 , 29 , 30 , and multiferroicity 31 – 34 . Additionally, large cryogenic MCEs in polycrystalline forms, such as GdCr 0.5 Fe 0.5 O 3 20 ( = 29.2 J/kg·K for ΔH = 0–4.5 T), Gd 2 NiMnO 6 35 ( = 37.2 J/kg·K for ΔH = 0–8 T), ErCr 0.5 Fe 0.5 O 3 36 ( = 12.4 J/kg·K for ΔH = 0–5 T), and DyCr 0.5 Fe 0.5 O 3 33 ( = 11.3 J/kg·K for ΔH = 0–4.5 T) have also been discovered. Various studies have hypothesized that large magnetic moments of magnetic rare-earth ions with strong anisotropy would significantly affect the cryogenic MCE.…”

Asymmetric magnetoimpedance effect and dipolar interactions of FINEMET/SiO2/FePd composite ribbons

“…Magnetic materials exhibit many new physical phenomena, such as magnetostriction (MS), [1] magnetocaloric effect (MCE), [2] giant magnetoresistance (GMR), [3] and giant magneto-impedance (GMI), which have rarely been studied. [4] Soft magnetic materials have been widely used due to their high saturation magnetization, low coercivity, and high permeability.…”