Magnetic oxides show a variety of extrinsic magnetotransport phenomena: grain-boundary-, tunnelling-and domain-wall magnetoresistance. In view of these phenomena the role of some magnetic oxides is outstanding: these are believed to be half-metallic having only one spin-subband at the Fermi level. These fully spinpolarized oxides have great potential for applications in spin-electronic devices and have, accordingly, attracted an intense research activity in recent years.This review is focused on extrinsic magnetotransport effects in ferromagnetic oxides. It consists of two parts; the second part is devoted to an overview of experimental data and theoretical models for extrinsic magnetotransport phenomena. Here a critical discussion of domain-wall scattering is given. Results on surfacial and interfacial magnetism in oxides are presented. Spin-polarized tunnelling in ferromagnetic junctions is reviewed and grain-boundary magnetoresistance is interpreted within a model of spin-polarized tunnelling through natural oxide barriers. The situation in ferromagnetic oxides is compared with data and models for conventional ferromagnets. The first part of the review summarizes basic material properties, especially data on the spin-polarization and evidence for half-metallicity. Furthermore, intrinsic conduction mechanisms are discussed. An outlook on the further development of oxide spinelectronics concludes this review.

The resistivity and magnetoresistance of a magnetite single crystal and Fe3 O4 films of various thicknesses were measured in the temperature range 70 K

We have investigated the magnetic properties of pure ZnO thin films grown under N 2 pressure on a-, c-, and r-plane Al 2 O 3 substrates by pulsed-laser deposition. The substrate temperature and the N 2 pressure were varied from room temperature to 570°C and from 0.007 to 1.0 mbar, respectively. The magnetic properties of bare substrates and ZnO films were investigated by SQUID magnetometry. ZnO films grown on c-and a-plane Al 2 O 3 substrates did not show significant ferromagnetism. However, ZnO films grown on r-plane Al 2 O 3 showed reproducible ferromagnetism at 300 K when grown at 300-400°C and 0.1-1.0 mbar N 2 pressure. Positron annihilation spectroscopy measurements as well as density-functional theory calculations suggest that the ferromagnetism in ZnO films is related to Zn vacancies.

The magnetic interlayer coupling in La0.7Sr0.3MnO3/SrRuO3 superlattices was investigated. High quality superlattices with ultrathin La0.7Sr0.3MnO3 and SrRuO3 layers were fabricated by pulsed laser deposition. The superlattices grew coherently with Mn/Ru intermixing restricted to about one interfacial monolayer. Strong antiferromagnetic interlayer coupling depended delicately on magnetocrystalline anisotropy and intermixing at interfaces. Ab initio calculations elucidated that the antiferromagnetic coupling is mediated by the Mn-O-Ru bond. The theoretical calculations allowed for a quantitative correlation between the total magnetic moment of the superlattice and the degree of Mn/Ru intermixing.

Real‐time ferroelectric polarization switching in magnetite epitaxial thin films is reported, proving that magnetite is not only historically the first material showing magnetism and correlated electron properties, but also that it is ferroelectric with a value of the ferroelectric polarization approaching that of well‐known ferroelectric materials such as BaTiO3.

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Magneto-optic studies of ZnO doped with transition metals Co, Mn, V and Ti indicate a significant magnetic circular dichroism (MCD) at the ZnO band edge at room temperature, together with an associated dispersive Faraday rotation. Similar spectra occur for each dopant which implies that the ferromagnetism is an intrinsic property of the bulk ZnO lattice. At 10 K additional paramagnetic contributions to the MCD are observed, but above about 150K, the magnitude of the MCD signal is dominated by the ferromagnetism and is almost temperature independent. The MCD at the ZnO band edge shows room temperature hysteretic behaviour. DOI: PACS numbers: 75.50 Pp, 75.50 Pp, The search for spintronic materials that combine semiconducting and ferromagnetic properties, dilute magnetic semiconductors (DMS), is currently the most topical field in magnetism. The compounds based on the wide-gap (3.4 eV) semiconductor ZnO are especially exciting because they exhibit ferromagnetism at room temperature [1][2][3][4][5][6], in contrast to the GaMnAs-based materials for which the highest reported Curie temperatures, T c , are still well below 300 K.Despite the growing body of evidence in favour of room temperature magnetic hysteresis in doped ZnO, the nature of the ferromagnetism is hotly contested. The original interest in ZnO was prompted by the prediction that the hole exchange mechanism found in GaMnAs would produce Curie temperatures above 300 K [7]. However, it is now known that the doping is normally n-type, for which the exchange is smaller [8]. Furthermore, the measured moments are often much smaller than the theoretical values, which suggests that the magnetism might be due to an impurity phase [9,10]. It is therefore highly important to carry out careful experimental studies that can elucidate the microscopic origin of the magnetism.In this Letter we present a detailed study of the magnetooptical (M-O) properties of ferromagnetic ZnO, together with other experimental details. A measurement of the magnetic circular dichroism (MCD) at photon energy E gives the difference in absorption for left and right circularly polarised light at that same energy. Hence it provides a clear indication of the extent to which the states involved in the transition at that particular energy are influenced by the magnetism. We concentrate here on the spectral region close to the band edge at ~3.4 eV, since this characterizes the intrinsic behaviour of the ZnO lattice. The results show that the ferromagnetism at 300K is intimately connected with the band electrons of ZnO and that the carriers are polarised. Furthermore, since ZnO is transparent in the blue/UV, the large Faraday rotations that we observe around 3 eV are potentially useful for applications in M-O processing.The Zn 1−x M x O samples studied here (M = transition metal) were grown as thin films by pulsed laser deposition (PLD) on sapphire (0001) substrates. Co, Mn, V and Ti were used as the dopants with concentrations up to 5%. An undoped ZnO film was also grown for reference. SQ...