X-ray detected ferromagnetic resonance (XFMR) spectroscopy is an experimental technique for element-specific spin dynamics in the GHz regime and has been utilized to study spintronic materials. The XFMR signal is usually obtained by detecting X-ray excited optical luminescence (XEOL) emitted from a sample substrate. Here, we report the development of an XFMR spectrometer that is designed to place a photodetector for XEOL detection outside an ultra-high-vacuum chamber. This configuration allows for the easy replacement of detectors, such as photodiodes, CCD cameras, and spectrometers, depending on the experimental requirements. We demonstrated the measurement of XEOL spectra from MgO using a visible light spectrometer as well as the detection of XFMR signals originating from the spin precession of a permalloy (Ni₈₀Fe₂₀) thin film using a photodiode detector. The XFMR spectrometer with an out-of-vacuum photodetector expands possibilities for advanced measurements such as XFMR microscopy.

  We analyze the influence of an oblique writing field on writability in 4 Tbpsi shingled heat-assisted magnetic recording employing a stochastic calculation. We confirm the result by employing a micromagnetic simulation. We focus on the mean magnetization reversal number per unit time 𝑁_ for the medium in the recording direction during writing to analyze the cause. Although erasure-before-write is independent of the writing field angle, erasure-after-write increases as the writing field angle 𝜙 measured from the perpendicular increases due to the large 𝑁_ value after the field writing time. The 1/𝑁_ value represents the mean time between stochastically induced magnetization reversals under thermal agitation. We introduce the medium writing time 𝜏_med, which is the time range where the 𝑁_ value is larger than 1 ns^-1. Write-error decreases as the 𝜙 value increases, since the 1/𝑁_ value becomes shorter and the 𝜏_med value becomes longer as the 𝜙 value increases. The same bit error rate bER for an oblique writing field can be obtained at a smaller writing field magnitude compared with a writing field perpendicular to the medium plane. Therefore, the minimum bER values are almost the same regardless of 𝜙.

  We investigate the dependence of the structure, magnetic properties, and longitudinal spin Seebeck effect (LSSE) voltage on the Fe composition (X) in Co_3-XFe_XO₄ (CFO) films prepared via co-precipitation and spin-coating on a Si substrate, where X is varied from 0.53 to 1.98. The crystal structure of the CFO films shows the spinel structure, whereas the Lotgering factor, which is related to the orientation distribution of crystal-oriented polycrystallines, indicates the maximum values at 0.72 ≤ X ≤ 1.17 and decreases at 1.38 ≤ X ≤ 1.98. The saturation magnetization (M_S) and effective anisotropy of the CFO films increase with X. The LSSE constant (S) of the CFO films increases with increasing X, and the maximum value of |S| is 5.9 × 10^-3 μV K^-1 at X = 1.81. The trend in |S| with increasing X is attributed to the enhancement of M_S which affects the magnon density, and to the reduction of thermal conductivity which affects the temperature gradient.

  The accidental collapse of concrete structures due to rebar corrosion can be a serious problem. Although electromagnetic induction is advantageous among the non-destructive testing methods, the depth and diameter of the rebar need to be measured in advance. In our previous study, multi-axis and multi-channel magnetic measurements were effective in estimating the rebar corrosion level, which could be done without requiring information on the depth of the rebar thanks to using a convolutional neural network (CNN). However, information on the rebar diameter was still needed. In the current study, we investigate how to estimate the corrosion level without depth and diameter information when inputting data combining the magnetic amplitude at three different diameters of rebar arrangements. To achieve this, we propose using cubic function interpolation to increase the amount of training data for the CNN. Our results showed that the accuracy of corrosion level estimation without cubic function interpolation was 82%, whereas when the interpolation was implemented at depths of 20, 25, 30, 40, and 50 mm, the accuracy rose to 89%. These findings demonstrate that the proposed method is effective in estimating the rebar corrosion level without information on the rebar depth and diameter.