Nanomechanical AC susceptometry of an individual mesoscopic ferrimagnet

Abstract

A novel method for simultaneous detection of both DC and time-dependent magnetic signatures in individual mesoscopic structures has emerged from early studies in spin mechanics. Multifrequency nanomechanical detection of AC susceptibility and its harmonics highlights reversible nonlinearities in the magnetization response of a single yttrium iron garnet (YIG) element, separating them from hysteretic jumps in the DC magnetization.

Nanocavity optomechanical torque magnetometry and radiofrequency susceptometry

“…The high detection sensitivity of resonant nanomechanical torque sensors has allowed for minimally-invasive observations of magnetostatic interactions and hysteresis in a variety of magnetic materials including thin films [15], mesoscale confined geometries that are deposited [16] or epitaxially grown [17], and small aggregates of nanoparticles [18]. Going beyond the static limit, nanomechanical torque magnetometry has been extended to timescales allowing for detection of slow thermally-activated dynamics [12], AC susceptibility [17], and magnetic resonance [19,20].This powerful technique relies upon detection of the deflection of a mechanical element by angular momentum transfer originating from magnetic torques τ = µ 0 m×H, generated as the magnetic moments in the system, m, experience an orthogonally-directed component of the applied magnetic field, H. So far, improvements to torque magnetometers have been driven primarily by enhancements to the response of nanomechanical resonators resulting from their low mass and high mechanical quality factor (Q m ). Readout of magnetically driven motion has involved detection through free-space optical interferometric methods with very low optical quality factor (Q o ≈ 1) Fabry-Perot cavities formed between the nanomechanical resonator its supporting substrate [16].…”

“…Torque magnetometry has seen recent resurgence owing to miniaturization of mechanical devices [14]. The high detection sensitivity of resonant nanomechanical torque sensors has allowed for minimally-invasive observations of magnetostatic interactions and hysteresis in a variety of magnetic materials including thin films [15], mesoscale confined geometries that are deposited [16] or epitaxially grown [17], and small aggregates of nanoparticles [18]. Going beyond the static limit, nanomechanical torque magnetometry has been extended to timescales allowing for detection of slow thermally-activated dynamics [12], AC susceptibility [17], and magnetic resonance [19,20].…”

Electric-Field Coupling to Spin Waves in a Centrosymmetric Ferrite

“…Particularly, the interaction between an electric field and a spin wave provides fundamental insight into the coupling between charge and spin degrees of freedom in a solid. Detection of this interaction at room temperature in single-crystal yttrium iron garnet (Y 3 Fe 5 O 12 , YIG), a material of great interest for magnonic device design because of its exceptionally low damping rate for spin waves [5] and rich linear and nonlinear properties [6][7][8][9][10][11][12][13][14], has proved difficult due to the lack of spontaneous electric polarization in YIG [15]. The presence of a center of inversion symmetry in single-crystal YIG prevents it from responding to applied electric fields via the same mechanism as materials such as frustrated magnets or multiferroics [16][17][18][19].…”

The Einstein - de Haas effect at radio frequencies in and near magnetic equilibrium

“…This intrinsic feature indicates a softening of the spin texture just before nucleation, and could also be thermally assisted. Spin texture softening has been observed before in magneto-optical susceptibility measurements arrays of permalloy disks 26 and in torque-mixing susceptometry of a YIG disk 27 .…”