We studied the Curie temperature T_C variation in L1₀-type FePt ordered alloys that were partially substituted with other transition metal elements, such as Mn, Cu, Ru, and Rh, by first-principles calculations. For the theoretical evaluation of T_C, a disordered local moment approach based on the coherent potential approximation was employed. The calculated results reveal that the most significant reduction in T_C was observed for FePt where some Pt was substituted by Ru, while a large uniaxial magnetic anisotropy constant on the order of 10⁷ erg/cm³ was maintained. An analysis of the electronic structure demonstrates that the stability of the ferromagnetic state is degraded by the substitution of Ru.

  In microwave assisted magnetic recording (MAMR), it is still a challenge to obtain stable oscillation of magnetization in the spin torque oscillator (STO). In this paper we point out that one possible problem in practical MAMR heads is oscillation disturbance by transmitted spins from the head poles, i.e. the main pole and trailing shield, and also discuss the requirements for good STO oscillation. We propose structure design candidates with a short spin-diffusion length material and with a negative spin-polarization material to obtain a larger microwave assist field generated from the STO using micromagnetics simulation.

  We developed ferrimagnetic [Co(0.5)/Gd(1)/Pt(1)]_N (unit: nm) multilayers with structural inversion symmetry breaking and investigated the dependence of magnetic properties and magnetic domain structures on the repetition number (N = 1 – 50). The magnetization compensation temperature increases as N increases, and saturates at around 210 K for N ≥ 20. All films with various repetition number possess the out-of-plane magnetic easy axis, and multi domain structure at the remanence state was observed in the film with N = 50. These results show that the magnetic properties of the ferrimagnetic Co/Gd/Pt multilayers can be tuned by the repetition number.

  This paper presents millimeter-scale small magnetic shields for electrical components such as magnetic sensors or magnetic random-access memories (MRAM). A prototype of a shielded package consisting of two shield pieces is fabricated by using a MEMS package assembly line. The shielded package exhibits anisotropic magnetic shielding effectiveness (MSE). Two magnetic circuit models are introduced to explain the cause of the anisotropic MSE. The models reveal that magnetic flux flow and magnetic reluctances are changed by an external magnetic field, which causes anisotropic MSE.

  Generating a magnetic field with a desired magnitude and direction in a plane by using a mangle-type magnetic field source with four permanent magnets is discussed. Two rotation patterns were compared by using a 2D finite element method in terms of the controllability of the magnetic field and the uniformity of the generated magnetic field. In both patterns, the arrangement of magnets that generates the maximum magnetic field corresponds to a Halbach cylinder. It was found that one of the rotation patterns is superior for controlling the magnitude and direction of the magnetic field independently, while it is inferior in terms of uniformity. Finally, the above findings were demonstrated with a prototype, although a slight deviation was seen between the simulation and the demonstration.