Negative differential magnetization for Ni nanoparticles in Al

Abstract

Using a layer-by-layer deposition technique, Ni thin films were sandwiched between AlO x layers in an Al matrix. By using x-ray-absorption spectroscopy, grazing incidence small-angle x-ray scattering, and highresolution transmission electron microscopy, we showed that the Ni layers are discontinuous and that pure Ni clusters are formed with sizes in the nanometer range. Depending on the preparation conditions, different magnetic behaviours are observed. When only one discontinuous Ni layer is grown, the hysteresis loops at low temperature display a conventional shape with a reduced magnetic moment per atom due to a magnetically dead layer at the cluster surface. When three discontinuous Ni layers are grown, a negative differential magnetization is observed. This phenomenon is interpreted as due to an antiferromagnetic coupling between two populations of magnetic grains having different average diameters in the different Ni layers. The coupling is indirect through the Al spacer.

Magnetic Transition and Large Magnetocaloric Effect Associated with Surface Spin Disorder in Co and CocoreAgshell Nanoparticles

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Magnetoelectric interaction and transport behaviours in magnetic nanocomposite thermoelectric materials

“…The M r and H C of MNC45 are remarkably greater than those of the matrix but much lower than those of BaM-NPs, which are about 9.7×10 -4 emu/g and 136 Oe, respectively. The negative differential magnetization in both the matrix and MNC45 under high magnetic field revealed a typical feature of field-induced antiferromagnetic coupling, as reported in discontinuous Ni nanoparticles in Al matrix 40 . Theoretically, since the c axis of BaM is the easy magnetization direction, an effective magnetocrystalline anisotropy field (H A ) parallel to the c axis is generated in BaM-NPs (Figure S6a) (Figure S6b).…”

Advanced optical magnetic nanostructures fabricated by anodic aluminum oxide membranes and magnetic fluids

“…Magnetic nanosized materials display a variety of unusual hysteresis loops, for the explanation of which several different models and possible physical mechanisms have been proposed. [29][30][31][32][33] Here, we discuss briefly the possible origin of the anomalous behavior compared with the conventional MF.…”