We have combined neutron scattering and piezoresponse force microscopy to show that the exchange field in $\mathrm{CoFeB}/{\mathrm{BiFeO}}_3$ heterostructures scales with the inverse of the ferroelectric and antiferromagnetic domain size of the ${\mathrm{BiFeO}}_3$ films, as expected from Malozemoff’s model of exchange bias extended to multiferroics. Accordingly, polarized neutron reflectometry reveals the presence of uncompensated spins in the ${\mathrm{BiFeO}}_3$ film at the interface with CoFeB. In view of these results, we discuss possible strategies to switch the magnetization of a ferromagnet by an electric field using ${\mathrm{BiFeO}}_3$.

We study the magnetic behavior of ${\mathrm{Fe}}_3{\mathrm{O}}_4\left(111\right)$ thin films with thicknesses between $5\mathrm{nm}$ and $50\mathrm{nm}$. The films are epitaxially grown on $\alpha \text{−}{\mathrm{Al}}_2{\mathrm{O}}_3\left(0001\right)$ single crystals by atomic-oxygen-assisted molecular beam epitaxy. The ${\mathrm{Fe}}_3{\mathrm{O}}_4\left(111\right)$ thin films exhibit high structural order with sharp interfaces and low roughness and exhibit a Verwey transition for thicknesses above $8\mathrm{nm}$. However, the samples have magnetic properties that deviate from the bulk ones. The magnetic moment varies between $2.4{\mu }_B$ for $5\text{−}\mathrm{nm}$-thick film and $3.2{\mu }_B$ for $50\text{−}\mathrm{nm}$-thick film in a field of $1.2\mathrm{T}$, which is lower than that of bulk samples ($4.1{\mu }_B∕{\mathrm{Fe}}_3{\mathrm{O}}_4$ formula). Still the magnetic saturation is never reached, even in fields as large as $2T$. The thinner the film, the slower the approach to saturation. Structural analysis, performed using high-resolution transmission electron microscopy, reveals the presence of antiphase boundaries (APB’s), the density of which decreases when the thickness increases. Using a model of ferromagnetic domains separated by antiferromagnetically sharp interfaces, we show that the slow approach to saturation observed in the films as a function of thickness is driven by the APB density.

The magnetic, transport, and structural properties of $({\mathrm{La}}_{\mathrm{0.1}}{\mathrm{Sr}}_{\mathrm{0.3}}{\mathrm{)MnO}}_{\mathrm{3}}$ films deposited on MgO (001) are reported as a function of thickness and substrate temperature. The substrate temperature is fundamental in determining the structural properties and a deviation from the optimum temperature (680 °C) leads to grain boundaries and an imperfect (001) texture. Films with different thicknesses were deposited at the optimum deposition temperature. Magnetization and resistivity measurements on these films are interpreted in terms of magnetic and electric “dead” layers. The electric dead layer is an insulating layer approximately 4 nm thick while the magnetic dead layer is a region of weakly coupled noncollinear spins approximately 10 nm thick at each interface.

We present the fabrication of metallic magnetic nanowires using a low temperature chemical process. We show that pressed powders and magnetically oriented samples exhibit a very high coercivity (6.5kOe at 140K and 4.8kOe at 300K). We discuss the magnetic properties of these metamaterials and show that they have the suitable properties to realize “high temperature magnets” competitive with AlNiCo or SmCo permanent magnets. They could also be used as recording media for high density magnetic recording.

The resistance generated by individual domain walls is measured in a FePd nanostructure. Combining transport and magnetic imaging measurements, the intrinsic domain wall resistance is quantified. It is found positive and of a magnitude consistent with that predicted by models based on spin scattering effects within the walls. This magnetoresistance at a nanometer scale allows a direct counting of the number of walls inside the nanostructure. The effect is then used to measure changes in the magnetic configuration of submicron stripes under application of a magnetic field.