Spin dynamics and frequency dependence of magnetic damping study in soft ferromagnetic FeTaC film with a stripe domain structure

Abstract

Perpendicular magnetic anisotropy (PMA) and low magnetic damping are the key factors for the free layer magnetization switching by spin transfer torque technique in magnetic tunnel junction devices. The magnetization precessional dynamics in soft ferromagnetic FeTaC thin film with a stripe domain structure was explored in broad band frequency range by employing micro-strip ferromagnetic resonance technique. The polar angular variation of resonance field and linewidth at different frequencies have been analyzed numerically using Landau-Lifshitz-Gilbert equation by taking into account the total free energy density of the film. The numerically estimated parameters Landé g-factor, PMA constant, and effective magnetization are found to be 2.1, 2×10 5 erg/cm 3 and 7145 Oe, respectively. The frequency dependence of Gilbert damping parameter (α) is evaluated by considering both intrinsic and extrinsic effects into the total linewidth analysis. The value of α is found to be 0.006 at 10 GHz and it increases with decreasing precessional frequency.Spin transfer torque (STT) has grater credibility compared to other techniques towards ultrafast spin dynamics in ferromagnet by electric current induced magnetization reversal of spin valves and magnetic tunnel junctions (MTJ). 1 The current researchers are more keen to focus on STT technology for its high density magnetic random access memories (MRAM), 2,3 STT-driven domain wall devices 4 and perpendicular magnetic recording media 5 applications. In order to make this technology more efficient, lowering the critical current density is essential which requires the material specifications with low saturation magnetization (M S ), high spin polarization, large uniaxial perpendicular magnetic anisotropy (PMA) constant and low magnetic damping. [6][7][8] The magnetic damping parameter (α) can be described well by the phenomenological Landau-Lifshitz-Gilbert equation and is known as the Gilbert damping. 9,10 Several attempts have been made for understanding the origin of Gilbert damping in spin dynamics relaxation in single layer as well as multilayered magnetic alloys, which arises from both intrinsic and extrinsic parts of the material. The intrinsic contribution to the Gilbert damping parameter has been studied by tuning the strength of the spin-orbit coupling. 8,11,12 Recently, Ikeda et al. 13 have reported that CoFeB-MgO based MTJ with PMA would be reliable for high-density non-volatile memory application due to its high thermal stability and efficiency towards STT technology. The investigation on magnetic dynamics, PMA and the apparent magnetic damping have been studied extensively in CoFeB based soft ferromagnetic thin film by ferromagnetic resonance (FMR) and timeresolved magneto-optical Kerr effect. 14,15 Malinowski et al. 16 have reported a large increase in Gilbert damping with applied magnetic field in perpendicularly magnetized CoFeB thin film.

Achievement of Diverse Domain Structures in Soft Magnetic Thin Film through Adjusting Intrinsic Magnetocrystalline Anisotropy

“…3 which is a signature of the formation of the stripe domain structure. According to the reported literatures, the film thickness possessing the stripe domain is about several hundred nanometers and the stripe domain comes from the weak perpendicular magnetic anisotropy that resulted from a stain and microstructure effect [8, 13, 19–22]. Its critical thickness can be described by …”

Ferromagnetic resonance studies of strain tuned Bi:YIG films

“…Thin film lattice constant (a ⊥ ) differs due to lattice mismatch between substrate and film (shown by vertical up arrows). This lattice mismatch causes rhombohedral distortion in the films and hence contributes to diagonally stretched unit cells along the [111] growth direction. The strain induced rhombohedral distortion in these epitaxial BiYIG films can be quantified using the parameter σ = (a b − a ⊥ )/a b = ∆a/a b , where, a b is the bulk BiYIG lattice parameter and a ⊥ is the stretched film lattice parameter along the [111] direction [2][3] [64].…”

“…This lattice mismatch causes rhombohedral distortion in the films and hence contributes to diagonally stretched unit cells along the [111] growth direction. The strain induced rhombohedral distortion in these epitaxial BiYIG films can be quantified using the parameter σ = (a b − a ⊥ )/a b = ∆a/a b , where, a b is the bulk BiYIG lattice parameter and a ⊥ is the stretched film lattice parameter along the [111] direction [2][3] [64]. For set-A samples, XRD patterns show strain relaxation as the thickness increases from 10.2 to 200 nm (2θ value approaches the bulk value), the strain-induced lattice distortion decreases from | 1.162% | to almost ∼| 0.0% |.…”

“…To probe the static and dynamic magnetic properties of BiYIG epitaxial films, we performed angular and frequency dependent FMR measurements on both the sets of samples. Generally, the magnetic garnet thin films with a hard axis in the [111] direction (i.e., In-plane easy axis), possesses extrinsic uniaxial magnetic and intrinsic magnetocrystalline cubic anisotropies. FMR can directly deduce the magnetic anisotropies in a precise manner.…”

“…4(b) for set-A and set-B are E ani = (−1.84±0.87)×10 3 +(11.17± 0.51)×10 6 [(a b −a ⊥ )/a b ] (erg/cm 3 ) and E ani = (−16.24± 4.31) × 10 3 + (7.76 ± 1.20) × 10 6 [(a b − a ⊥ )/a b ] (erg/cm 3 ), where the slope of the lines give −b = (11.17±0.51)×10 6 (erg/cm 3 ) and −b = (16.24 ± 4.31) × 10 6 (erg/cm 3 ), respectively. The negative sign of b implies that the magnetic easy axis is parallel to the compressed lattice plane; [111]. The magnetoelastic constant of BiYIG comes out to be larger than in pure-YIG film [2].…”