Yamaguchi Yasuo

Magnetic Structure of SrFeO3

A neutron diffraction study was carried out on SrFeO 3 . The results indicate that the magnetic structure is a helical one with the helicoid vector k ; k // and | k |=0.112 a * . The Fe 4+ magnetic moment is 2.7±0.4 µ B at liquid nitrogen temperature.

Magnetic Structure of SrCoO2.5

SrCoO 2.5 with brownmillerite (4CaO·Fe 2 O 3 ·Al 2 O 3 ) type structure is an antiferromagnet with the Neel temperature of 570 K. The magnetic structure as determined from a neutron diffraction study is of G-type and the Co 3+ magnetic moment is 3.3±0.5µ B at liquid nitrogen temperature.

Neutron Diffraction Study on MnPS3 and FePS3

Neutron diffraction study on the layer compounds MnPS 3 and FePS 3 reveals a collinear antiferromagnetic order, respectively, below T N =78 K and 120 K with the corresponding wave vectors k =[000] and [\(00\frac{1}{2}\)], the magnetic moments pointing to the direction perpendicular to the layer planes for both cases. The intralayer exchange parameters between first ( J 1 ), second ( J 2 ) and third nearest neighbors ( J 3 ) are all antiferromagnetic for MnPS 3 , whereas for FePS 3 J 1 is ferromagnetic and J 2 and J 3 are antiferromagnetic, all of which have the same sign as those for the respective selenium compounds, but the absolute values are a bit larger in the sulfides than in the selenides.

Antiferromagnetism of Fe1+δSb

Fe 1+δ Sb (0.08≤δ≤0.38) crystallizes in the NiAs structure, and the excess Fe atoms occupy the interstitial positions. The Mossbauer effect measurements show that at liquid nitrogen temperature and below, an antiferromagnetic order sets in, and the internal magnetic field at liquid helium temperature amounts to 106 kOe. The Neel temperature, however, is not discernible in the susceptibility measurements. The susceptibility shows a maximum at around 20 K, whose origin is supposed to be due to spin ordering of excess Fe atoms.

Polarized Neutron Diffraction Study of a CuCr2Se4 Single Crystal

The electronic state of CuCr 2 Se 4 is investigated by means of the polarized neutron diffraction technique. From the measured form factors of copper and chromium atoms, the magnetic moments are determined to be -0.07±0.02 (µ B /Cu) and 2.64±0.04 (µ B /Cr), respectively. Further, the uniform polarization existent throughout the crystal is estimated to be -0.20±0.11 µ B per formula unit, using the total moment 5.01±0.01 (µ B /CuCr 2 Se 4 ) obtained from the magnetization measurement. This result which differs from those reported by other authors with neutron diffraction, shows that neither of the ionic configuration models of Cu + [Cr 3+ Cr 4+ ]Se 4 and Cu 2+ [Cr 3+ 2 ]Se 4 gives a satisfactory explanation of CuCr 2 Se 4 , although the former is closer to the experimental data. The form factor of the chromium atom agrees well with the calculated free ion form factor for Cr + , but not for Cr 3+ , and this fact indicates that the unpaired electron density on the chromium atom is more spread than that for fr...

Magnetic Structure of Fe1+δSb

The magnetic structure of the NiAs-type intermetallic compound, Fe 1+δ Sb, with \(0.08{\lesssim}\delta{\lesssim}0.64\) was determined by means of neutron diffraction. Below the Neel point (105 K), magnetic superstructure lines corresponding to the triangular spin arrangement in the basal plane of hexagonal lattice are observed. The temperature dependence of the intensity of the magnetic superstructure lines was studied in the temperature range from 10 K to 117 K, and the temperature dependence of the Fe atomic moment can be fitted to the Brillouin function of spin 1/2. The moment of the normal site Fe atom is estimated to be 0.88±0.05µ B at 10 K.

Neutron Scattering Study on the Orbital Order of DyB2C2 in Magnetic Fields

Antiferroquadrupolar (AFQ) ordering in DyB 2 C 2 has been investigated by neutron scattering under applied magnetic fields. In the AFQ ordered phase, antiferromagnetic reflections indexed as 1,0,1/2, 1,0,1 and 1,0,3/2 appear upon applying magnetic fields, and develop with fields up to 2.5 T. These field induced AFM reflections are clear evidence of the AFQ order in DyB 2 C 2 . Experimental result shows that the induced magnetic dipolar moments are strongly suppressed by the AFQ order of the Dy quadrupolar moments. A possible model of this magnetic ordering is proposed.

Magnetic Anisotropy of Cr1-xTe with x=0.077

The temperature dependence of the direction of the easy axis of magnetization in the ferromagnetic compound Cr 1- x Te ( x =0.077, T c =342 K) is determined by single crystal magnetic and neutron diffraction measurements in the temperature range from 80 K to 350 K. Below about 200 K the spin direction lies in the c -plane, but with the rise of temperature it stands up gradually towards the c -axis. At 293 K the spin lies in a direction intermediary between c -axis and c -plane. The result is not in accord with Hirone et al. s according to which the anisotropy axis lies along the c -axis all the way from liquid helium temperature to room temperature. The discrepancy is attributed to the difference in x between their sample and ours.

Antiferroquadrupolar Ordering in DyB 2C 2 Studied by 161Dy Mössbauer Spectroscopy

161 Dy Mossbauer effects were measured on the tetragonal antiferroquadrupolar ordered compound DyB 2 C 2 . In the magnetic phase below T C =15.3 K, the Mossbauer spectra are interpreted well by a single set of hyperfine parameters which gives the Dy magnetic moment of 9.0 µ B . The hyperfine field anomalously decreases below T C as temperature decreases, which can be interpreted as symmetry frustration between antiferromagnetic and antiferroquadrupolar interactions acting on Dy 3+ ions. Reflecting the 4 f electronic state in which two Kramers doublets locate with a low-energy separation, the spectra in the antiferroquadrupolar ordered phase and paramagnetic phase are complicated and cannot be well analyzed by the two-level relaxation model with a single set of hyperfine parameters, although it is supposed that the Dy electronic state is one type.

Anomalous Magnetic Susceptibility of Antiferromagnetic TbB2C2

We measured the magnetic susceptibilities of TbB 2 C 2 under fields along the , and directions. The susceptibilities below T N exhibit clear twofold symmetry in the (0 0 1) plane. No spontaneous magnetization in TbB 2 C 2 indicates that this anisotropy in the tetragonal basal plane reflects parallel and perpendicular susceptibilities of an antiferromagnet. The susceptibilities of the and [1 1 0] directions show no cusp-like anomaly but anomalous upturns below T N with decreasing temperature, though TbB 2 C 2 is confirmed to be an antiferromagnet.