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Magnetoplumbite-(M)-type hexaferrites are the most widely used base materials of permanent magnets. La–Co substitution in these M-type Sr hexaferrites improves these magnetic anisotropies. By 57 Fe Mössbauer spectroscopy using the single-crystalline samples, we have investigated the Fe electronic states in the La–Co substituted M-type Sr hexaferrites, Sr 1 − x La x Fe 12 − y Co y O 19 , as a function of an external magnetic field to discuss the enhancement of these magnetic anisotropies. All observed 57 Fe Mössbauer spectra were well analyzed using the five subspectra corresponding to the five crystallographic nonequivalent Fe sites. At one site of these five Fe sites, the 2 a Fe site, the extracted hyperfine interaction parameters clearly show the Co substitution and external magnetic field dependences, revealing the increments of the 3 d electrons in the Fe ions, which are caused by the substitution of Co 2 + ions for Fe 3 + ions at the neighbor 4 f 1 Fe site. This hybridization between the Fe ions and the Co ions induces the non-negligible unquenched orbital momentum in the Fe ions at the 2 a Fe site. Our findings represent an enhancement of the magnetic anisotropies in Sr 1 − x La x Fe 12 − y Co y O 19. [ABSTRACT FROM AUTHOR]

In the ferrite magnets, the magnetoplumbite-type strontium hexaferrite (SrFe12O19) is an important base material with a relatively high Curie temperature. The La-Co substitution in the Sr hexaferrites ((Sr,La)(Fe,Co)12O19) significantly improves magnetic coercivity. We have investigated the electronic states of Sr1-xLaxFe12-yCoyO19 by 57Fe Mössbauer and Co Kβ x-ray emission spectroscopies using the single-crystalline samples. The Co Kβ x-ray emission spectrum shows that all Co2+ ions are in the high-spin state. The hyperfine parameters extracted from the observed 57Fe Mössbauer spectra clearly show the Co and La substitution dependences at two Fe sites of the five crystallographically nonequivalent Fe sites, revealing that most Co2+ ions occupy the 4f1 and 2a Fe sites in Sr1-xLaxFe12-yCoyO19. These Co site occupations are consistent with the higher magnetic coercivity without a decrease in remanent magnetization in the La-Co substituted Sr hexaferrites. [ABSTRACT FROM AUTHOR]

We studied the phase stability of Ce-substituted magnetoplumbite-type Sr ferrite under various oxygen pressures. We have successfully obtained Ce-substituted samples as revealed from X-ray diffraction and wavelength dispersion X-ray analyses. The solubility limit of Ce in Sr1-xCexFe12O19 was estimated to be $x = 0.24$ at ambient pressure, which is reduced to 0.05–0.10 under higher oxygen pressures. The variation of the $c$ -axis against $x$ and the reduction of the solubility by increasing oxygen pressure suggests that the valence of Ce is not 4+ but 3+. The solubility limit of Ce is dominated not only by the ionic radius but also by the valence instability of Ce. [ABSTRACT FROM AUTHOR]

The Fe Mössbauer spectra of the single crystalline and the finely ground SrLaFeCoO ( x = 0 : y = 0, x = 0.192 : y = 0.152 and x = 0.456 : y = 0.225) samples have been measured to investigate the La-Co substitution effects. All observed spectra at 150 K were well fitted using the five subspectra which correspond to the five crystallographical nonequivalent Fe sites in the M-type hexaferrite, indicating that the valence changes to Fe ions in the Fe ions were not observed in our SrLaFeCoO samples. In SrFeO, the relative absorption intensities in the five subspectra show the large anisotropies in the recoilless fractions at the five Fe sites whereas these anisotropies were not observed in SrLaFeCoO. These results indicate the chemical compositional dependence on the anisotropies of the recoilless fractions at the five Fe sites. The substitution of a Co ion for the Fe ion changes the center shifts of the Fe ions near the Co ion by the perturbation of the Fe-O-Co hybridizations. Therefore, the Co ions occupy the 4 f and the 4 f sites due to the chemical compositional dependences of the refined magnetic hyperfine field and center shifts of the Fe ions. [ABSTRACT FROM AUTHOR]

51V nuclear magnetic resonance and relaxation are reported for the Hollandite Bi1.77V8O16 system. BixV8O16 having the Hollandite structure with 1.6 exhibits a metal–insulator transition (MIT) in the range 1.72 We have measured the spin–lattice relaxation rate 1/T1 of 51V NMR to investigate the magnetic and electric properties of Bi1.77V8O16, which will provide information on the electronic states below and above the MIT temperature TMIT in this system. Above TMIT, the temperature dependence of 1/T1T obeys a modified Korringa relaxation with a large correlation factor K(α)=3.2, implying that the antiferromagnetic spin fluctuations are dominant in the metallic regime of the present system. [Copyright &y& Elsevier]

Abstract: We found the field-induced magnetic ordering for a quasi-one-dimensional alternating spin chain compound Pb2V3O9, which can be understood by Bose–Einstein condensation of triplons. In this paper, we present the temperature-field magnetic phase diagram, which is drawn from magnetic susceptibility, high field magnetization and 51V NMR measurements. [Copyright &y& Elsevier]

Single crystals of the shandite-type half metallic ferromagnet Co 3 Sn 2 S 2 , and its In-substituted compounds, Co 3 Sn 2− x In x S 2 (0< x ≤2) were grown by a flux method. We report optimum conditions to synthesize large crystals. Single crystals of the two end members, Co 3 Sn 2 S 2 and Co 3 In 2 S 2 , and solid solutions with low In concentrations ( x ≤0.35) were grown out of Sn and In self flux. Solid solution single crystals with higher In concentrations were grown out of Sn, In and Pb mixture flux. Grown crystals were characterized using the powder x-ray diffraction, wavelength-dispersive x-ray spectroscopy and magnetization measurements. The shandite structure with R 3̄ m symmetry was confirmed and crystal structure parameters of the obtained plate-shaped hexagonal crystals were refined using the Rietveld analysis. Magnetization measurements show suppression of the ferromagnetic ordering, observed in Co 3 Sn 2 S 2 , by In-substitution as reported for polycrystalline samples. The obtained crystals are useful to study anisotropy in magnetic and transport properties and further interesting magnetotransport properties of the layered compounds. [ABSTRACT FROM AUTHOR]

ScFe 6 Ge 4 with the LiFe 6 Ge 4 -type structure (space group R 3 ¯ m), which has a double-layered kagome lattice (18 h site) of Fe crystallographically equivalent to that of a well-known topological ferromagnet Fe 3 Sn 2 , is newly found to be antiferromagnetic (AFM) with a high Néel temperature of T N ≈ 650 K, in contrast to the ferromagnetic (FM) ground state previously proposed in a literature. 45Sc nuclear magnetic resonance experiment revealed the absence of a hyperfine field at the Sc site, providing microscopic evidence for the AFM state and indicating AFM coupling between the bilayer kagome blocks. The stability of the AFM structure under the assumption of FM intra-bilayer coupling is verified by DFT calculations. • LiFe 6 Ge 4 -type ScFe 6 Ge 4 is a double-layered kagome antiferromagnet. • The Néel temperature is as high as 650 K. • In-bilayer ferromagnetic and inter-bilayer antiferromagnetic couplings were proposed. • The stability of the antiferromagnetic structure was verified by DFT calculations. • ScFe 6 Ge 6 is an antiferromagnetic alternative to the topological magnet Fe 3 Sn 2. [ABSTRACT FROM AUTHOR]

Abstract: We studied the 2D NMR spectrum on the novel superconductor . The temperature dependence of Knight shift at 2D in the normal state is parallel to that of magnetic susceptibility and the hyperfine coupling constant is estimated as . The resonance frequency in the low temperatures does not change below , which is contrast to that in 59Co site. [Copyright &y& Elsevier]

Abstract: We performed 59Co NMR and NQR measurements of superconductor with of about 5K in order to decide the pairing symmetry of the Cooper pairs. From NQR measurements, it was found that the increase in above is attributed to nearly ferromagnetic fluctuations. The spin contributed Knight shift was estimated by vs. plot. Consequently, the Knight shift below is invariant at 7T. This result suggests the possibility of unconventional superconductivity with the spin-triplet state of p- or f-wave pairing symmetry. [Copyright &y& Elsevier]