V. V. Naletov

Generation of coherent spin-wave modes in yttrium iron garnet microdiscs by spin-orbit torque.

In recent years, spin–orbit effects have been widely used to produce and detect spin currents in spintronic devices. The peculiar symmetry of the spin Hall effect allows creation of a spin accumulation at the interface between a metal with strong spin–orbit interaction and a magnetic insulator, which can lead to a net pure spin current flowing from the metal into the insulator. This spin current applies a torque on the magnetization, which can eventually be driven into steady motion. Tailoring this experiment on extended films has proven to be elusive, probably due to mode competition. This requires the reduction of both the thickness and lateral size to reach full damping compensation. Here we show clear evidence of coherent spin–orbit torque-induced auto-oscillation in micron-sized yttrium iron garnet discs of thickness 20 nm. Our results emphasize the key role of quasi-degenerate spin-wave modes, which increase the threshold current.

Dynamics of two coupled vortices in a spin valve nanopillar excited by spin transfer torque

We investigate the dynamics of two coupled vortices driven by spin transfer. We are able to independently control with current and perpendicular field and to detect the respective chiralities and polarities of the two vortices. For current densities above J=5.7×107 A/cm2, a highly coherent signal (linewidth down to 46 kHz) can be observed, with a strong dependence on the relative polarities of the vortices. It demonstrates the interest of using coupled dynamics in order to increase the coherence of the microwave signal. Emissions exhibit a linear frequency evolution with perpendicular field, with coherence conserved even at zero magnetic field.

Full control of the spin-wave damping in a magnetic insulator using spin-orbit torque.

A. Hamadeh, O. d’Allivy Kelly, C. Hahn, H. Meley, R. Bernard, A.H. Molpeceres, V. V. Naletov, 2, 3 M. Viret, A. Anane, V. Cros, S. O. Demokritov, J. L. Prieto, M. Muñoz, G. de Loubens, and O. Klein ∗ Service de Physique de l’État Condensé (CNRS URA 2464), CEA Saclay, 91191 Gif-sur-Yvette, France Unité Mixte de Physique CNRS/Thales and Université Paris Sud 11, 1 av. Fresnel, 91767 Palaiseau, France Institute of Physics, Kazan Federal University, Kazan 420008, Russian Federation Department of Physics, University of Muenster, 48149 Muenster, Germany Instituto de Sistemas Optoelectrónicos y Microtecnoloǵıa (UPM), Madrid 28040, Spain Instituto de Microelectrónica de Madrid (CNM, CSIC), Madrid 28760, Spain (Dated: May 30, 2014)

Conduction of spin currents through insulating antiferromagnetic oxides

Damping processes, associated to magnetization dynamics, allow to generate spin currents from precessing ferromagnets. These can be transmitted into adjacent conducting layers through an interface exchange interaction with conduction electrons. It is in principle also possible to inject angular momentum into insulators but the relevant physical mechanisms are not yet identified. In order to test some ideas concerning pure spin transport through insulating oxides, the present paper reports on the behaviour of two materials with very different properties: NiO is an antiferromagnet whereas SiO2 is a non-magnetic light element insulator. While a sizeable flow of angular momentum is found to be able to propagate through nickel oxide, a SiO2 layer as thin as 2 nm completely blocks this transfer. This underlines some essential features required to conduct a spin current, including the presence of either magnetic order through which magnons can propagate, or compounds with large spin-orbit interactions where phonons can carry angular momentum.

Ferromagnetic resonance force spectroscopy of individual submicron-size samples

We review how a magnetic-resonance force microscope (MRFM) can be applied to perform ferromagnetic resonance spectroscopy of individual submicron-size samples. We restrict our attention to a thorough study of the spin-wave eigenmodes excited in Permalloy (Py) disks patterned out of the same 43.3-nm-thin film. The disks have a diameter of either 1.0 or

Efficient Synchronization of Dipolarly Coupled Vortex-Based Spin Transfer Nano-Oscillators.

0.5\text{ }\ensuremath{\mu}\text{m}

Magnetic resonance studies of the fundamental spin-wave modes in individual submicron Cu/NiFe/Cu perpendicularly magnetized disks.

and are quasisaturated by a perpendicularly applied magnetic field. It is shown that quantitative spectroscopic information can be extracted from the MRFM measurements. In particular, the data are extensively compared with complementary approximate models of the dynamical susceptibility: (i) a two-dimensional analytical model, which assumes a homogeneous magnetization dynamics along the thickness, and ii) a full three-dimensional micromagnetic simulation, which assumes a homogeneous magnetization dynamics below a characteristic length scale

Detection of Microwave Spin Pumping Using the Inverse Spin Hall Effect

c

Identification and selection rules of the spin-wave eigen-modes in a normally magnetized nano-pillar

and approximates the cylindrical sample volume by a discretized representation with regular cubic mesh of lateral size

Measurement of the dynamical dipolar coupling in a pair of magnetic nanodisks using a ferromagnetic resonance force microscope.

c=3.9\text{ }\text{nm}