Fe-N thin films are prepared on MgO(001) single-crystal substrates at temperatures ranging from room temperature to 600 °C by varying the ratio of N₂ partial to total pressure in sputtering from 0 to 5%. The effects of substrate temperature and N₂ partial pressure ratio on the formation of γʹ phase (sc-based L’1 phase) are systematically investigated. Epitaxial α phase (bcc-based A2 phase) is formed in the films prepared by sputtering in pure Ar gas for all the investigated temperatures. On the other hand, the structure is delicately influenced by the substrate temperature when the films are prepared in Ar-N₂ mixture gases. Epitaxial films are obtained at temperatures higher than 300 °C, whereas the films prepared at temperatures lower than 200 °C involve poly-crystals. When the N₂ partial pressure ratio is 2.5%, the films prepared at temperatures ranging between 200 and 400 °C consist of a mixture of α and γʹ phases and the volume fraction of γʹ phase decreases with increasing the substrate temperature. When the N₂ partial pressure ratio is 5%, γʹ single-crystal films are obtained at temperatures ranging from 300 to 400 °C. The N site ordering parameter slightly increases as the substrate temperature increases from 200 to 400 °C. The films prepared at temperatures higher than 500 °C in the N₂ partial pressure ratios of 2.5 and 5% primarily consist of α phase. The present study has shown that high substrate temperature prevents the formation of γʹ phase and employment of a moderate substrate temperature around 300–400 °C is suitable to obtain a γʹ single-crystal film.

  Electrical equivalent circuit parameters of a microstrip line (MSL) with a Co-Zr-Nb film as a noise suppressor were estimated by magnetic circuit analysis. First, the magnetic flux distribution in the cross section of the MSL with Co-Zr-Nb film was theoretically calculated to determine the magnetic flux path of the magnetic circuit. Second, the circuit parameters were calculated by the magnetic circuit analysis and compared with the values obtained by S-parameter measurement. The results are in good agreement, which indicates the feasibility of the estimation of the electrical equivalent circuit parameters of the MSL with the noise suppressor using the magnetic circuit analysis with the cross-sectional dimensions and material properties.

  Magnetic Particle Imaging (MPI) is an imaging modality that directly detects the nonlinear response of magnetic nanoparticles (MNPs). Spatial encoding is realized by saturating MNPs almost everywhere except in the vicinity of a special point called the field free point (FFP) using a static magnetic field. Recently, it has been shown that the sensitivity of MPI can be significantly improved using a simultaneous encoding scheme by scanning with a field free line (FFL) instead of FFP. The MPI with FFL device was developed using a neodymium magnet and an iron yoke to image the object with small amount of magnetic nanoparticle such as in biological systems. The magnetization response of magnetic nanoparticles in biological systems was studied using the developed MPI device. We developed the imaging system that can evaluate the magnetic signal and relaxation time of magnetic moments which is reflected by core and hydrodynamic size of MNPs. We found that iron concentration changes the MNP size, and then the relaxation time is varied.