Spin-up conversion, exchange-interactions, and tailored magnetic properties in core-shell La2NiMnO6of small crystallites

Abstract

La₂NiMnO₆-a ferromagnetic (FM) insulator offers tunable charge carriers and spins useful to devise its multiple properties and applications. In this view, we studied a core-shell La₂NiMnO₆(2-3 nm shell on 65 - 80 nm core) of a Ni²⁺/Ni³⁺(d⁷) to Mn⁴⁺/Mn³⁺(d⁴) spin-up conversion- revived a new FM phase-2, raising a spin-densityσ_s = 0.7 s a^-1over the Ni^2+/Mn⁴⁺species (phase-1),σ_s = 0.5 s a^-1, i.e. 2.12μ_B/f.u. larger spin moment. HRTEM images studied with x-ray diffraction characterizing core-shell structure that plays a crucial role in tuning the high spin FM phase-2 of profound properties. Below 110 K, the dc magnetization and ac magnetic susceptibilityχ(ω,T) reveal a metastable magnetic behavior on an antiferromagnetic canting of a spin-glass nature. The results follow a Vogel-Fulcher type relaxation with a relaxation timeτ₀∼ 10^-13s, confirming a spin-glass freezing behavior. Uniquely, FM field of phase-1 controls magnetics of phase 2 of a coupled magnet, modulating joint features with small thermal magnetic hysteresis on heating-cooling cycles.

Keywords: core-shell crystallites; exchange-coupled magnets; lattice images; magnetic properties; magnetic transitions; spin-cluster; spin-glass.