Bismuth-doped Yttrium iron garnet (Bi:YIG) thin films known for large magneto-optical activity with low losses still need to get probed for its magnetization dynamics. We demonstrate a controlled tuning of magnetocrystalline anisotropy in Bi-doped Y3Fe5O12 (Bi:YIG) films of high crystalline quality using growth induced epitaxial strain on [111]-oriented Gd3Ga5O12 (GGG) substrate. We optimize a growth protocol to get thick highly-strained epitaxial films showing large magnetocrystalline anisotropy, compare to thin films prepared using a different protocol. Ferromagnetic resonance measurements establish a linear dependence of the out-of-plane uniaxial anisotropy on the strain induced rhombohedral distortion of Bi:YIG lattice. Interestingly, the enhancement in the magnetoelastic constant due to an optimum substitution of Bi 3+ ions with strong spin orbit coupling does not strongly affect the precessional damping (∼ 1.15 × 10 −3 ). Large magneto-optical activity, reasonably low damping, large magnetocrystalline anisotropy and large magnetoelastic coupling in BiYIG are the properties that may help BiYIG emerge as a possible material for photo-magnonics and other spintronics applications.

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.

No abstract

The crystal structure, magnetic structure, and magnetic properties of Nd1-xNaxMnO3 (x = 0, 0.15, and 0.20) compounds were studied using magnetization and neutron powder diffraction techniques. The magnetic ordering is found to undergo a transition from A-type antiferromagnetic (AFM) structure for x = 0 to pseudo charge-exchange (CE)-type AFM phase for x = 0.20 through the spin canted ferromagnetic (FM) phase for x = 0.15. Two magnetic transitions at 75 K and 15 K were observed for x = 0 sample and are ascribed to AFM ordering of Mn ions and ferrimagnetic ordering of Nd ions, respectively. In the case of x = 0.15, a canted FM ordering at around 80 K and a pseudo CE-type AFM magnetic structure at 5 K were observed. The x = 0.20 sample exhibits a charge-ordering transition at 180 K followed by a spin-glass like transition at around 40 K. The magnetic structure of x = 0.20 sample below 125 K is found to be pseudo CE-type AFM structure. The propagation vectors associated with Mn3+ and Mn4+ sublattices are (0 0 ½) and (½ 0 ½), respectively. The maximum refined magnetic moments of Mn3+ and Mn4+ ions in x = 0.20 sample are found to be 3.20 μB and 3.00 μB, respectively.

No abstract