Ichiro Tsubokawa

On the Magnetic Properties of the System MnSb-CrSb

The change of magnetic properties due to the replacement of manganese by chromium in manganese antimonide (MnSb), which is of the NiAs structure, was investigated. It was found that, with the increase of the concentration of chromium, the magnetic behaviour of these compounds (Mn 1- x Cr x )Sb changes as follows: (1) at x =0 (MnSb), the temperature-magnetization curve shows typical behaviour of ferromagnetic substance, (2) in the range 0.1≤ x ≤0.7, it deviates remarkably from the Weiss curve in proportion with the chromium content, and the temperature dependence of the reciprocal susceptibility above the Curie point is of a ferrimagnetic type. (3) In the range 0.8≤ x ≤0.9 a transition from ferrimagnetic to antiferromagnetic was observed, and finally (4) at x =1 (CrSb) a typical antiferromagnetism could be seen. A short discussion of such transitions is given.

On Nickel Oxides of High Oxygen Content

Nickel oxides of high oxygen content formed by incomplete dissociation of nickel nitrate were investigated crystallographically and magnetically. The oxygen excess of these oxides ranges from zero to 0.2 gr. atom/mol., and their crystal structures are not essentially different from that of the ordinary nickel oxide. As they are not in a stable state, they have some curious but important behaviors. That is, with the degree of excess, they become to have a cubic structure the parameter of which is larger than that ( a ) of a rhombohedrally deformed one, and at sufficiently high oxygen contents they behave as something like a ferromagnetics. Such rather extraordinary phenomena may be considered to be originated from the fact that the oxygen excess in the specimens owes not only nickel vacancies but also the absolute excess of anions. In the measurements of susceptibility, the coincidency between the heating and cooling curves is very good for ferromagnetics-like oxides, while it is not for antiferromagnetic ...

On the Magnetic Properties of Nickel Sulfide

Magnetic measurements were performed on the specimens of powdered and single crystals of nickel sulfide having the structure of nickel arsenide type. From the results of measurements of the susceptibility, specific heat and other data, it was found that nickel sulfide is antiferromagnetic with the Neel point at 150°K. However, below 120°K, the susceptibility of the powder specimen increased with the fall of temperature and also showed a dependence of magnetic field. Such a rise in susceptibility at lower temperatures is here interpreted as due to the influence of paramagnetic islands. Correction for the atom core diamagnetism was applied to the observed susceptibilities, and from the inverse susceptibility vs temperature relation, the Curie constant per mol. C M the spin quantum number, S , and the asymptotic Curie temperature, θ, were obtained as 0.89, 1.9/2 and ca 3000° respectively. From the torque measurement of a single crystal of this compound, it was seen that the antiferromagnetic easy direction l...

On the Magnetic Properties of Vanadium Sulfide and Selenide

Magnetic, thermal and crystallographic properties of sulfide as well as selenide of vanadium with nickel arsenide structure were investigated experimentally. The antiferromagnetic Neel points for these compounds were found to be about 1040° and 163° K respectively. A correction for the atom core diamagnetism was applied to the observed susceptibilities; the inverse susceptibility decreased linearly with the fall of temperature. Based on this result, the Curie constant, C M , the spin quantum number, S and the asymptotic Curie temperature, θ, were obtained as 1.63, 2.9/2 -3000° for sulfide and 2.15, 3.2/2 and -2570° for selenide respectively. Anomalous heat absorptions at the magnetic transition in both compounds were 615 and 50 cal/mol respectively. Experimental results obtained are discussed briefly.

The Magnetic Properties of Chromium-Tellurium-Selenium System

The change of magnetic properties due to the replacement of tellurium by selenium in CrTe, which has NiAs structure, was investigated. Ferrcomagnetism is observed in the concentration range from x =0 to x =0.8, where x is defined by Cr(Te 1- x Se x ). The compounds outside this range are para- or antiferromagnetic. In the paramagnetic range of temperature the Curie-Weiss law is found to be valid. It was also found that the Curie-Weiss constant is independent of concentration in the neighbourhood of CrTe and CrSe respectively, and varies abruptly at the transition concentration from ferro-to antiferromagnetic state. A short discussion are given.

The Magnetic Properties of Single Crystals of Chromium Selenide

The magnetic susceptibilities of the single crystals as well as powder specimen of chromium selenides with the composition, CrSe 1.00 , CrSe 1.04 and CrSe 1.07 were measured from the boiling point of liquid helium up to 900°K. The susceptibility vs. temperature curves showed a break at 279°K, 271°K and 232°K for CrSe 1.00 , CrSe 1.04 and CrSe 1.07 respectively. The anisotropy of the susceptibility increases rapidly from these breaking points to lower temperatures. There exists also a peak of the specific heat just above the room temperature which, however, lies a little higher than the breaking point mentioned above. This peak temperature of specific heat is considered to be the antiferromagnetic Neel point. Asymptotic Curie temperature, θ p , Curie constant C M and spin quantum number S were determined from the susceptibility data in the paramagnetic region.

Some Physical Properties of Nickel Oxides

Variation of the magnetic susceptibility, electric resistivity and specific heat with temperature have been observed for various nickel oxides containing different amounts of copper. The anomaly temperatures of these properties and also of their lattice generally differ from one another. Among these temperatures the last one is the lowest and the magnetic one is the highest, and the higher is the copper content the larger is the difference. It may be concluded from these results that the deformation of nickel oxide must be originated from the antiferro-magnetic exchange interaction as proposed by Greenwald and Smart, 4) but at the same time it seems to be affected by the other factors e.g. the ionic radius ratio and the vacancies.

Magnetic Anisotropy of Chromium Antimonide and its Manganese Substitites

Magnetic anisotropy of compounds of CrSb, (Cr 0.9 Mn 0.1 )Sb and (Cr 0.8 Mn 0.2 )Sb was investigated by using their single crystals. From the measurements of torque curves by means of torsion pendulum magnetometer, the difference between the susceptibilities parallel and perpendicular to the c -axis of the hexagonal crystal lattice was obtained for each specimen. It was confirmed that the magnetic spin axis lies along the c -axis for each compound. (also in the ferrimagnetic region of (Cr 0.8 Mn 0.2 )Sb) The magnetic anisotropy constant K of CrSb was estimated to be about 10 5 erg/gr. at room temperature.