Uniform hexagonal single phase Ni1–x Fe x O (x = 0, 0.01, 0.05, and 0.1) nanoparticles synthesized by a standard hydrothermal method are characterized with an enhanced lattice expansion along with a decrease in the microstrain, crystal size, and Ni occupancy as a function of the Fe concentration. The observed anomalous temperature and field dependent magnetic properties as a function of the Fe content were explained using a core–shell type structure of Ni1–x Fe x O nanoparticle such that the effect of Fe-doping has led to a decrease of disordered surface spins and an increase of uncompensated-core spins. Perfect incorporation of Fe3+ ions at the octahedral site of NiO was observed from the low Fe concentration; however, at a higher Fe content, 4:1 defect clusters (four octahedral Ni2+ vacancies surrounding an Fe3+ tetrahedral interstitial) are formed in the core of the nanoparticles, resulting in the transition of spin-glassy to the cluster-glassy system. An enhanced thermal magnetic memory effect is noted from the cluster-glassy system possibly because of increased intraparticle interactions. The outcome of this study is important for the future development of diluted magnetic semiconductor spintronic devices and the understanding of their fundamental physics.

Monoclinic CdWO4 is a member of the tungstate family with great potential in diverse applications. However, CdWO4 exhibits a diamagnetic property with a wideband gap of 3.7 eV, limiting its widespread applications. This study reports significant modulation of magnetic and optical properties of hydrothermally grown single-crystalline CdWO4 nanorods with controllable substitution of Cu2+ ions at the Cd2+ site. The chemical environment of Cu and the magnetic and luminescence of nanorods were thoroughly investigated using synchrotron-based powder X-ray diffraction, temperature-dependent photoluminescence, X-ray absorption, element selective X-ray excited optical luminescence spectroscopies, a magnetometer, and micro-Raman spectroscopy. The main feature of this study is an astonishing redshift of ∼0.8 eV in the bandgap energy accompanied by a relative ∼46% drop in the internal quantum efficiency and a progressive transition from diamagnetic to an enhanced magnetization concerning the Cu content. The experimental findings show that significant modulation in optical and magnetic properties is correlated with Cu-doping-induced intermediate energy states and [CuO6] ferromagnetic clusters. The outcome of this study provides important insight into designing doped nanomaterials for photocatalytic applications.

With the evolution of synthesis and the critical characterization of core-shell nanostructures, short-range magnetic correlation is of prime interest in employing their properties to develop novel devices and widespread applications. In this regard, a novel approach of the magnetic core-shell saturated magnetization (CSSM) cylinder model solely based on the contribution of saturated magnetization in one-dimensional CrO2/Cr2O3 core-shell nanorods (NRs) has been developed and applied for the determination of core-diameter and shell-thickness. The nanosized effect leads to a short-range magnetic correlation of ferromagnetic core-CrO2 extracted from CSSM, which can be explained using finite size scaling method. The outcome of this study is important in terms of utilizing magnetic properties for the critical characterization of core-shell nanomagnetic materials.

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The search for diluted magnetic semiconductors (DMSs) has gained immense research interest because of the coexistence of the charge and spin degree of freedom in a single substance to realize a particular class of spintronic devices, and a rare earth (RE)-doped transition-metal oxide (TMO) is one of the choices. This study intends to understand the effect of RE Sm 3+ ion substitution in antiferromagnetic (AF) NiO nanoparticles (NPs) using modern cutting-edge techniques (synchrotron powder X-ray diffraction and soft X-ray absorption, Raman scattering, and superconducting quantum interference device magnetometry). A percolation threshold limit of about 1% incorporation of Sm 3+ ions at the Ni 2+ site was evident. An enhanced magnetic moment observed for an intermediate composition has been attributed to the interacting bound magnetic polaron. A core−shell model has been proposed such that the multivalent point defects reside at the surface of NPs, whereas the core of the particles retains AF properties. The exchange coupling mediated by interfacial frozen spins is the leading mechanism behind the magnetic memory effect at room temperature. The outcome of this study is vital for the future development of RE-functionalized TMO DMS spintronic devices and the understanding of their fundamental physics and chemistry.