We examine here the adjacent track interference (ATI) problem that arises when writing in an adjacent track for heat-assisted magnetic recording combined with shingled magnetic recording (shingled HAMR). For ATI, the bit error rate is a function of readout track width. We calculate the bit error rate and the minimum normalized readout field for various readout track widths. The factors affecting ATI are grain temperature and grain volume. We compare ATI and writing sensitivity for all combinations of 2 and 4 Tbpsi, and 6 and 9 grains/bit under the conditions of constant grain volume and constant grain height. For constant grain volume, 4 Tbpsi shingled HAMR is less advantageous than 2 Tbpsi shingled HAMR in terms of ATI due to the higher grain temperature caused by the smaller grain pitch. The grain number per bit must be lower and the grain height must be greater to be able to improve ATI for 4 Tbpsi shingled HAMR. We show there to be a loss of writing sensitivity for 4 Tbpsi shingled HAMR due to a statistical factor caused by the lower grain number per bit and the higher thermal stability factor resulting from the larger grain volume.

  To obtain a high magnetization Ca-Zn-based spinel ferrite, we investigated the synthesis conditions and magnetic properties of samples with compositions of Ca: Zn: Fe = 0.5: 2.5: 16-x (x = 1, 2, 3, 4, 5, 6, and 7) sintered at 1300°C and then cooled under different conditions (-200°C/hour or quenched in water). Quenching the sample at x = 3 resulted in the best sample with the highest magnetization of 146 emu/g at T = 1.8 K. We estimated the Fe²⁺ amount and molar ratio of the sample by using thermogravimetry/ differential thermal analysis (TG/DTA). The large lattice constant implied that the spinel contained Ca²⁺ ions at its transition metal sites, which possibly led to a cationic distribution contributing to the high magnetization.

  High saturation magnetization and perpendicular magnetic anisotropy are required for ferromagnetic / ferroelectric thin films to apply magnetic recording such as magnetic writing elements of magnetic wire memory, which is a next-generation device with very high recording density. To realize the magnetic properties, substitution of Co against Fe in (Bi_1-xBax)FeO₃ and (Bi_1-xLa_x)FeO₃ thin films were investigated. In the (Bi,Ba)(Fe,Co)O₃ thin films, both Ba and Co substitution up to several tens at% had contribution to increase the saturation magnetization. The high saturation magnetization was obtained in (Bi,Ba)(Fe,Co)O₃ thin films with the total composition of Ba and Co of around 60 at%. Further increment of Ba and Co substitution decreased the saturation magnetization because the formation of the BiFeO₃ phase is hindered by an excess amount of Ba and Co with larger ion radius than Bi and Fe. Co substitution up to 20 at% had contribution to increase the perpendicular magnetic anisotropy. In the (Bi,La)(Fe,Co)O₃ thin films, the effect of La substitution was not large to increase the saturation magnetization and perpendicular magnetic anisotropy, however the effect of Co substitution up to 30 at% was large to increase the saturation magnetization and perpendicular magnetic anisotropy.

  Ultra-compact electric vehicles (EV) have recently begun to be sold instead of general vehicles with gasoline engine to new transportation recently. However, as the outer plate of an ultra-compact EV has low rigidity, the road noise that a tire generates by rotation and the wind noise generated by the projection shape of the vehicle transmit to the inside. It is thought that this interior noise deteriorates ride comfort for passengers. Therefore, we have been investigating a system for actively controlling noise transmitted from the outside with control sound generated by a giant magnetostrictive actuator on the ceiling of the cabin instead of a speaker installed in the vehicle. The control sound forms a wall in the cabin. The giant magnetostrictive actuator is required to produce sufficient thrust, less distortion, and delayed sound waves. In this paper, we studied giant magnetostriction force and performed a frequency analysis on the frequency of the harmonics generated when 100 to 500 Hz of control sound was output.