Spin precession with frequencies up to 280 GHz is observed in ${\mathrm{Mn}}_{3-\delta }\mathrm{Ga}$ alloy films with a perpendicular magnetic anisotropy constant $K_u\sim 15\mathrm{M}\mathrm{erg}/{\mathrm{cm}}^3$. The damping constant $\alpha$, characterizing macroscopic spin relaxation and being a key factor in spin-transfer-torque systems, is not larger than 0.008 (0.015) for the $\delta =1.46$ (0.88) film. Those are about one-tenth of $\alpha$ values for known materials with large $K_u$. First-principles calculations well describe both low $\alpha$ and large $K_u$ for these alloys.

Transport properties in magnetic tunnel junctions (MTJs) with ${\text{Co}}_2{\text{Fe}}_x{\text{Mn}}_{1-x}\text{Si}$ $\left(\text{CFMS},x=0–1.0\right)/\text{Al}–\text{O}/{\text{Co}}_{75}{\text{Fe}}_{25}$ structure and Gilbert damping constant in the epitaxial CFMS films were investigated. The tunnel magnetoresistance ratio is as high as 75% in MTJs with $x=0.6$ at room temperature. The Gilbert damping constant is minimal at $x=0.4$ . Relations between half-metallicity and the Gilbert damping constant in CFMS films were examined, revealing that the damping constant is small in half-metallic CFMS films.

Cr, Mn, Co, Ni, and Cu were added to polycrystalline BiFeO3 films, and their influence on the ferroelectric, electrical, and magnetic properties was investigated. All the additives except Ni reduced the leakage current density in the high electric field region. The addition of Cu and Co decreased the coercive field without reducing remanent polarization. The addition of Co caused spontaneous magnetization at room temperature, which exhibited a large coercive field of 16kOe at 10K. It was revealed that Co addition suppressed the leakage current density, decreased the electric coercive field, and induced spontaneous magnetization and large magnetic coercivity.

We report on epitaxial growth and magnetic properties of ${\text{Mn}}_{2.5}\text{Ga}$ thin films, which were deposited on Cr/MgO single crystal substrates by magnetron sputtering. X-ray diffraction results revealed the epitaxial relationships as ${\text{Mn}}_{2.5}\text{Ga}\left(001\right)\left[100\right]\parallel \text{Cr}\left(001\right)\left[110\right]\parallel \text{MgO}\left(001\right)\left[100\right]$ . The presence of (002) and (011) superlattice peaks indicates that the films were crystallized into ${\text{DO}}_{22}$ ordered structures. The perpendicular magnetic anisotropy (PMA) properties were found to be related to the extent of ${\text{DO}}_{22}$ chemical ordering. A giant PMA $\left(K_u^{\text{eff}}=1.2\times {10}^7\text{erg}/{\text{cm}}^3\right)$ and low saturation magnetization $\left(M_s=250\text{emu}/{\text{cm}}^3\right)$ can be obtained for the film with highest chemical ordering parameter $\left(S=0.8\right)$ .

To investigate the correlation between perpendicular magnetic anisotropy and intrinsic Gilbert damping, time-resolved magneto-optical Kerr effect was measured in $\text{Pt}/\text{Co}\left(d_{\text{Co}}\right)/\text{Pt}$ films. These films showed perpendicular magnetization at $d_{\text{Co}}=1.0\text{nm}$ and a perpendicular magnetic anisotropy energy $K_u^{\text{eff}}$ that was inversely proportional to $d_{\text{Co}}$ . With an analysis based on the Landau–Lifshitz–Gilbert equation, the intrinsic Gilbert damping constant $\alpha$ was evaluated by parameter-fitting of frequency and lifetime expressions to experimental data of angular variations in spin precession frequency and life-times. The $\alpha$ values increased significantly with decreasing $d_{\text{Co}}$ but not inversely proportional to $d_{\text{Co}}$ .