Spin Hall magnetoresistance at Pt/CoFe2O4 interfaces and texture effects

We report magnetoresistance measurements on thin Pt bars grown on epitaxial (001) and (111) CoFe2O4 (CFO) ferrimagnetic insulating films. The results can be described in terms of the recently discovered spin Hall magnetoresistance (SMR). The magnitude of the SMR depends on the interface preparation conditions, being optimal when Pt/CFO samples are prepared in situ, in a single process. The spin-mixing interface conductance, the key parameter governing SMR and other relevant spin-dependent phenomena such as spin pumping or spin Seebeck effect, is found to be different depending on the crystallographic orientation of CFO, highlighting the role of the composition and density of magnetic ions at the interface on spin mixing.Comment: 13 pages, 5 figure

Multiphase magnetic deflagrations in a Nd5Ge3 single crystal

We report magnetic deflagration phenomena ocurring in both antiferromagnetic and ferromagnetic phases in a single crystal of the intermetallic compound Nd5Ge3. We have investigated, using a trigger heat pulse, the spatial and time-resolved evolution of induced magnetic avalanches as a function of the applied magnetic field. The experimental data fit well with the theory of magnetic deflagration

Competing effects at Pt/YIG interfaces: spin Hall magnetoresistance, magnon excitations and magnetic frustration

We study the spin Hall magnetoresistance (SMR) and the magnon spin transport (MST) in Pt/Y3Fe5O12(YIG)-based devices with intentionally modified interfaces. Our measurements show that the surface treatment of the YIG film results in a slight enhancement of the spin-mixing conductance and an extraordinary increase in the efficiency of the spin-to-magnon excitations at room temperature. The surface of the YIG film develops a surface magnetic frustration at low temperatures, causing a sign change of the SMR and a dramatic suppression of the MST. Our results evidence that SMR and MST could be used to explore magnetic properties of surfaces, including those with complex magnetic textures, and stress the critical importance of the non-magnetic/ferromagnetic interface properties in the performance of the resulting spintronic devices.Comment: 15 pages, 4 figure

Modulation of pure spin currents with a ferromagnetic insulator

We propose and demonstrate spin manipulation by magnetically controlled modulation of pure spin currents in cobalt/copper lateral spin valves, fabricated on top of the magnetic insulator Y$_3$Fe$_5$O$_{12}$ (YIG). The direction of the YIG magnetization can be controlled by a small magnetic field. We observe a clear modulation of the non-local resistance as a function of the orientation of the YIG magnetization with respect to the polarization of the spin current. Such a modulation can only be explained by assuming a finite spin-mixing conductance at the Cu/YIG interface, as it follows from the solution of the spin-diffusion equation. These results open a new path towards the development of spin logics.Comment: 5 pages and 4 figures + supplemental material (10 pages, 7 figures

Training the polarization in integrated La0.15Bi0.85FeO3-based devices

The functionalities of BiFeO3-based magnetoelectric multiferroic heterostructures rely on the controlled manipulation of their ferroelectric domains and of the corresponding net in-plane polarization, as this aspect guides the voltage-controlled magnetic switching. Chemical substitution has emerged as a key to push the energy dissipation of the BiFeO3 into the attojoule range but appears to result in a disordered domain configuration. Using non-invasive optical second-harmonic generation on heavily La-substituted BiFeO3 films, it is shown that a weak net in-plane polarization remains imprinted in the pristine films despite the apparent domain disorder. It is found that this ingrained net in-plane polarization can be trained with out-of-plane electric fields compatible with applications. Operando studies on capacitor heterostructures treated in this way show the full restoration of the domain configuration of pristine BiFeO3 along with a giant net in-plane polarization enhancement. Thus, the experiments reveal a surprising robustness of the net in-plane polarization of BiFeO3 against chemical modification, an important criterion in ongoing attempts to integrate magnetoelectric materials into energy-efficient device