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We investigate near-Fermi-energy (${E}_{F}$) element-specific electronic and spin states of ferromagnetic van der Waals (vdW) metal ${\mathrm{Fe}}_{5}\mathrm{Ge}{\mathrm{Te}}_{2}$. The soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) measurement provides spectroscopic evidence of localized Fe $3d$ band. We also find prominent hybridization between the localized Fe $3d$ band and the delocalized Ge/Te $p$ bands. This picture is strongly supported from direct observation of the remarkable spin polarization of the ligand $p$ bands near ${E}_{F}$, using x-ray magnetic circular dichroism (XMCD) measurements. The strength of XMCD signal from ligand element Te shows the highest value, as far as we recognize, among literature reporting finite XMCD signal for nonmagnetic element in any systems. Combining SX-ARPES and elemental selective XMCD measurements, we collectively point to an important role of giant spin polarization of the delocalized ligand Te states for realizing itinerant long-range ferromagnetism in ${\mathrm{Fe}}_{5}\mathrm{Ge}{\mathrm{Te}}_{2}$. Our finding provides a fundamental elemental selective viewpoint for understanding mechanism of itinerant ferromagnetism in low-dimensional compounds, which also leads to insight for designing exotic magnetic states by interfacial band engineering in heterostructures.

In this paper, a first-order complex filter realized by using a voltage follower is proposed. Applying equivalent transformations to a passive complex filter, a complex filter including a series circuit of a resistor and an inductor is obtained. This series circuit can be realized by using a voltage follower, a capacitor and resistors. The resulting circuit includes four resistors, two capacitors and a voltage follower only. The validity of the proposed method is confirmed through computer simulation.

[Formula: see the attached file] is one of the promising ferromagnetic semiconductors for spintronic device applications because its Curie temperature (Tc) is above 300 K when the Fe concentration x is equal to or higher than similar to ∼0.20. However, the origin of the high Tc in (Ga,Fe)Sb remains to be elucidated. To address this issue, we use resonant photoemission spectroscopy (RPES) and first-principles calculations to investigate the x dependence of the Fe 3d states in [Formula: see text] (x = 0.05, 0.15, and 0.25) thin films. The observed Fe 2p-3d RPES spectra reveal that the Fe-3d impurity band (IB) crossing the Fermi level becomes broader with increasing x, which is qualitatively consistent with the picture of double-exchange interaction. Comparison between the obtained Fe-3d partial density of states and the first-principles calculations suggests that the Fe-3d IB originates from the minority-spin (↓) e states. The results indicate that enhancement of the double-exchange interaction between e↓ electrons with increasing x is the origin of the high Tc in (Ga,Fe)Sb.

We report magnetization, specific heat, and NMR measurements of 3-Br-4-F-V [=3-(3-bromo-4-fluorophenyl)-1,5-diphenylverdazyl], a strong-rung S=1/2 Heisenberg spin ladder with ferromagnetic leg interactions. We explain the magnetic and thermodynamic properties based on the strong-rung regime. Furthermore, we find a field-induced successive phase transition in the specific heat and the nuclear spin-lattice relaxation rate 1/T1. 19F-NMR spectra for higher- and lower-temperature phases indicate partial magnetic order and incommensurate long-range order, respectively, evidencing the presence of frustration due to weak interladder couplings., 12 pages, 3 figures