Generation of megahertz-band spin currents using nonlinear spin pumping

Abstract

Spin pumping enables the generation of d.c. and gigahertz-band (GHz-band) voltages from an applied microwave via magnetization dynamics when combined with inverse spin Hall effects. However, generating such voltages in the in-between frequency region, or the megahertz (MHz) band, has been difficult since ferromagnetic resonance usually occurs in the GHz band. Here we show that in spite of GHz-band microwaves applied, MHz-band voltages can be generated by spin pumping with use of nonlinear magnetization dynamics in Y3Fe5O12. The mechanism is ascribed to the MHz-band oscillation of the amplitude of the magnetization precession, which is projected onto a rectified voltage component via spin pumping. The present finding could be useful for frequency down-conversion thanks to the simple and durable structure, continuous-wave operation, and the tunability of an output frequency with low magnetic fields.

Nutation Spectroscopy of a Nanomagnet Driven into Deeply Nonlinear Ferromagnetic Resonance

“…The nutation spectroscopy of magnetization thus allows a more detailed investigation of the highly nonlinear regime, where auto-oscillation instabilities [6,23,40,41] and instability patterns [42] have been evidenced. Moreover, its quantitative understanding, made possible thanks to the low density of SW modes in nanomagnets, should enable to test further the LLG equation governing the motion of magnetization against experimental measurements.…”

Spin excitations in laser-molecular-beam epitaxy-grown nanosized YIG films: towards low relaxation and desirable magnetization profile

“…Another area of activity, in which the low spin-wave relaxation is important, is the study of insulator YIG film / nonmagnetic metal (Pt) heterostructures [16][17][18][19][20][21]. The spins in the YIG film and electrons in the metal are coupled by a strong spinorbital interaction.…”

Magnetic properties, spin waves and interaction between spin excitations and 2D electrons in interface layer in Y3Fe5O12/AlO x /GaAs-heterostructures

“…At present, there is observed extensive studies of insulator YIG film/nonmagnetic metal (Pt) structures, in which spins in the YIG film and electrons in the metal are coupled by a strong spin-orbital interaction [23][24][25][26][27]. The spin-orbital interaction gives spin waves the opportunity to influence the current flowing in the metal and to generate spin waves by the direct electric current [23].…”

“…A strong enhancement of the spin-current emission is observed at low frequencies, showing the appearance of nonlinear phenomena [24]. In the absence the spin-orbital interaction, for example, in structures Pt/SiO 2 / YIG, spin-wave excitations do not influence on the current [26]. Nevertheless, it is noted that the microwave electromagnetic interaction between ferrites and stripline conductors are effectively used in magnetoelectronic devices such as bandpass filters [28,29].…”