Experimental observation of an enhanced anisotropic magnetoresistance in non-local configuration

We compare non-local magnetoresistance measurements in multi-terminal Ni nanostructures with corresponding local experiments. In both configurations, the measured voltages show the characteristic features of anisotropic magnetoresistance (AMR). However, the magnitude of the non-local AMR signal is up to one order of magnitude larger than its local counterpart. Moreover, the non-local AMR increases with increasing degree of non-locality, i.e., with the separation between the region of the main current flow and the voltage measurement region. All experimental observations can be consistently modeled in terms of current spreading in a non-isotropic conductor. Our results show that current spreading can significantly enhance the magnetoresistance signal in non-local experiments

Giant magnetic anisotropy changes in Sr2CrReO6 thin films on BaTiO3

The integration of ferromagnetic and ferroelectric materials into hybrid heterostructures yields multifunctional systems with improved or novel functionality. We here report on the structural, electronic and magnetic properties of the ferromagnetic double perovskite Sr2CrReO6, grown as epitaxial thin film onto ferroelectric BaTiO3. As a function of temperature, the crystal-structure of BaTiO3 undergoes phase transitions, which induce qualitative changes in the magnetic anisotropy of the ferromagnet. We observe abrupt changes in the coercive field of up to 1.2T along with resistance changes of up to 6.5%. These results are attributed to the high sensitivity of the double perovskites to mechanical deformation.Comment: 3 figure

High-Field Magnetoresistance of Microcrystalline and Nanocrystalline Ni Metal at 3 K and 300 K

The magnetoresistance (MR) and the magnetization isotherms were studied up to high magnetic fields at T = 3 K and 300 K for a microcrystalline ($\mu$c) Ni foil corresponding to bulk Ni and for a nanocrystalline (nc) Ni foil. At T = 3 K, for the $\mu$c-Ni sample with a residual resistivity ratio (RRR) of 331, the field dependence of the resistivity was similar to what was reported previously for high-purity ferromagnets whereas the MR(H) behavior for the nc-Ni sample with RRR = 9 resembled that what was observed at low temperatures for Ni-based alloys with low impurity concentration. In the magnetically saturated state, the resistivity increased with magnetic field for both samples at T = 3 K and the field dependence was dominated by the ordinary MR due to the Lorentz force acting on the electron trajectories. However, the MR(H) curves were found to be saturating for $\mu$c-Ni and non-saturating for nc-Ni, the difference arising from their very different electron mean free paths. At T = 300 K, the MR(H) curves of both Ni samples were very similar to those known for bulk Ni. After magnetic saturation, the resistivity decreased nearly linearly with magnetic field which behavior is due to the suppression of thermally-induced magnetic disorder with increasing magnetic field. The MR(H) data were analyzed at both temperatures with the help of Kohler plots from which the resistivity anisotropy splitting ($\Delta\rho_{AMR}$) and the anisotropic magnetoresistance (AMR) ratio were derived. It was demonstrated that at T = 300 K, $\rho(H\rightarrow 0)=\rho(B\rightarrow 0)$ due to the negligible contribution of the ordinary MR. The data for the two Ni samples at 3 K and 300 K were found to indicate an approximately linear scaling of $\Delta\rho_{AMR}$ with the zero-field resistivity. This implies that the AMR ratio does not vary significantly with temperature in either microstructural state of Ni.Comment: 57 pages, 19 figure

Scaling behavior of the spin pumping effect in ferromagnet/platinum bilayers

We systematically measured the DC voltage V_ISH induced by spin pumping together with the inverse spin Hall effect in ferromagnet/platinum bilayer films. In all our samples, comprising ferromagnetic 3d transition metals, Heusler compounds, ferrite spinel oxides, and magnetic semiconductors, V_ISH invariably has the same polarity. V_ISH furthermore scales with the magnetization precession cone angle with a universal prefactor, irrespective of the magnetic properties, the charge carrier transport mechanism or type. These findings quantitatively corroborate the present theoretical understanding of spin pumping in combination with the inverse spin Hall effect

Scaling behavior of the spin pumping effect in ferromagnet/platinum bilayers

We systematically measured the DC voltage V_ISH induced by spin pumping together with the inverse spin Hall effect in ferromagnet/platinum bilayer films. In all our samples, comprising ferromagnetic 3d transition metals, Heusler compounds, ferrite spinel oxides, and magnetic semiconductors, V_ISH invariably has the same polarity. V_ISH furthermore scales with the magnetization precession cone angle with a universal prefactor, irrespective of the magnetic properties, the charge carrier transport mechanism or type. These findings quantitatively corroborate the present theoretical understanding of spin pumping in combination with the inverse spin Hall effect