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A flight of magnetization steps for increasing temperature has been made by making use of the compounds Mn2−xCrxSb, which are well known to undergo a first-order antiferromagnetic-to-ferrimagnetic phase transition for increasing temperature with the transition temperature increasing as x increases. A linear slope of magnetization for increasing temperature is also obtained in a wide temperature region of 60K for a compound Mn2−xCrxSb with a heterogeneous Cr distribution in the crystal. Temperature hysteresis at the first-order transition temperature is observed for three samples with different Cr compositions. A brief discussion about some potential applications of the magnetic characteristics is given on the basis of the experimental data.

Local spin magnetic moments of Co, Ni, and La atoms and their dependences on the crystal volume in the compounds LaCo5, LaNi5, and LaCo3Ni2 are calculated by two methods of the self-consistent linear muffin-tin orbital (LMTO) within the atomic sphere approximation and the full potential LMTO. The generalized gradient approximation is taken into account for the calculation of the crystal volume in the nonmagnetic state. Calculated results by these methods are compared to each other. It is found that there is no significant difference between the calculation results for the compounds LaCo5, LaNi5, and LaCo3Ni2 in this work and those for the compounds YCo5, YNi5, and YCo3Ni2 reported previously by other authors.

An X-ray generator consists of a negative high-voltage power supply and a field-emission-type cold-cathode X-ray tube. The tube is a glass-enclosed diode utilizing a transmission-type molybdenum target with a thickness of 20 µm, a needle graphite (carbon) cathode, a glass tube body, and a 0.5-mm-thick beryllium window. The tube current decreases gradually with time. After aging for 30 minutes, the tube current was approximately 0.2 mA with a tube voltage of 25 kV, and the focal-spot dimensions were 2.2×1.6 mm. Characteristic X-rays of molybdenum K-series were obtained after penetrating the molybdenum target and the beryllium window, and the K-absorption edge was observed clearly. The generator produced number of K photons was approximately 4×106 photons/cm2·s at 1.0 m from the source. The average photon energies of Kα and Kβ lines were 17.4 and 19.6 keV, respectively, and quasi-monochromatic radiography was performed using a computed radiography system.

We present specific heat measurements of the title compounds and discuss the results in connection with their magnetic properties.

Magnetic measurements have been performed at T = 5 K in a high magnetic field up to 150 kOe for powdered and field-oriented samples of Gd 1− x Dy x Co 4 B with 0 ≤ x ≤ 0.75. Magnetocrystalline anisotropy of the rare earth sublattice in the CeCo 4 B type structure is discussed on the basis of the experimental data.

The ground state of Sm 3+ in the intermetallics with transition metal (M) has been investigated on the basis of the uniaxial crystalline electric field (CEF) and molecular field by taking account of excited J multiplets up to the highest level. When the second order CEF term A 2 0 is negative, with increasing A 4 0 , the Sm magnetic moment initially increases and then suddenly becomes negative, i.e. antiparallel to the M moment. Detailed inspection of the eigenvalues and eigenfunctions has revealed that this sudden reversal of Sm moment is caused by the crossing of energy levels |J = 5 2 , M J = − 5 2 〉 and |J = 5 2 , M J = − 3 2 〉 .

CeCo 4 B is found to undergo an isostructural transition which is strongly dependent on the pressure. A huge magnetic anisotropy exists in a wide temperature regime extending even above Curie temperature.

Magnetization curves have been measured at T = 4.2 K for field-aligned samples of compounds LaCo 4 B and Y n + 1 Co 3 n + 5 B 2 n with n = 1, 2 and 3, in a pulsed high magnetic field up to 35 T. Magnetocrystalline anisotropy constants K 1 have been estimated and discussed for the compounds mentioned above.

Thermal expansion and magnetic susceptibility were measured for the compounds CrAs 1− x S x ( x ⩽ 0.20). The large spontaneous magnetostriction of CrAs, which occurs mainly along the B -axis of the orthorhombic MnP-type structure, decreases monotonously with the composition x and seems to disappear at x = 0.35. The susceptibility measurements for CrAs 0.84 S 0.16 show the crystallographic phase transition accompanied by a magnetic phase change at about 800 K.

Ce 2 Co 7 B 3 orders ferromagnetically below 250 K. AC-susceptibility and low dc-field measurements reveal the strong domain wall pinning indicating a large magnetocrystalline anisotropy. At higher fields a metamagnetic transition from a low to a high magnetization state occurs in a wide temperature regime concomitant with a large hysteresis below 150 K.

Magnetic measurements for RCo 4 M (M-B, Al and Ga; R-Y, Nd and Ho) have been done in order to compare the M-substitution effects on the magnetic properties of RCo 5 . In the case of M-B, the crystal structure is of CeCo 4 B-type, while in the case of M-Al and Ga, it is of CaCu 5 -type. By the B substitution for the Co of RCo 5 the magnetic anisotropy of the R sublattice is enhanced for R-Nd, while it seems to be weakened for R-Ho. The Co and R sublattice magnetizations and the exchange interaction between them are also discussed.

The spin reorientation temperatures and some other magnetic properties have been measured and discussed for the systems Pr 1− x Nd x Co 4 Al (0≤ x ≤1), NdCo 4− x Fe x Al (0≤ x ≤1.5), Nd 1− x Sm x Co 4 Al(0≤ x ≤1) and Nd 1− x Dy x Co 4 Al (0≤ x ≤1).

The field-induced transition from a low spin state to a high spin state in Mn1−xCrxAs is studied. A driving force of the transition is attributed to an exchange interaction of itinerant electrons enhanced by forced magnetostriction.

S substitution for As of CrAs compound has been successful up to 90 at. % for the first time in this work. The x‐ray powder patterns and magnetic susceptibility curves have been observed for the compounds CrAs1−xSx(0≤x≤0.6) in the temperature region from 80 K to 1100 K. It was found that the crystallographic transition from the orthorhombic MnP to the hexagonal NiAs type structure occurs with increase of temperature in the composition region x≤0.5. From the temperature dependence of lattice parameters, large spontaneous magnetostriction is found to occur mainly along the B axis of the compounds with small x. The magnetostriction decreases with x and disappears at x=0.35. The Neel temperature have also been determined. The magnetic moments per Cr atom in the compounds with x=0.3, 0.4, and 0.5 have been found to be within 2.95±0.10 μB, in the temperature region of the NiAs type structure. These data are compared with the previous ones of similar compounds.

Magnetization process of the intermetallic compound Fe 2- x Mn x As is investigated under a high magnetic field up to 560 kOe with a special interest in the metamagnetic behaviors both in the antiferromagnetic and ferrimagnetic states. Two kinds of stepwise transitions are found and the observed field-induced transitions are attributed to the step magnetizations of the site-I moment where two kinds of magnetic instabilities appear under a high magnetic field. The moment increases of Fe and Mn spins of two metamagnetic states are quantitatively determined.

The system Mn 2 Sb (1- x ) As ( x ) (0≦ x ≦1) is found to be solid solutions of the Cu 2 Sb type by X-ray analysis. A magnetic phase diagram has been produced by magnetic measurments in the temperature range 80 to 1100 K. Transition from antiferromagnetic to ferrimagnetic states with increasing temperature was observed for the compounds with x ≦0.4 and the compounds with x ≧0.55 were antiferromagnetic at all temperatures below the Neel temperatures. It is shown that these magnetic transition are explained qualitatively by the molecular field theory.

The crystallographic parameters of compounds MnAs 1- x P x (0≦ x ≦0.275) are determined as a function of temperature between about 100 and 600 K. It is found that these crystals except for MnAs take a MnP type structure in low temperature side and transform to a NiAs type at critical temperatures. These structural transitions are of second kind and accompanied with very large dilation (∼10%) of crystal volume. In order to see the relationship between the structural and magnetic properties, the temperature variation of magnetic susceptibilities of the compounds is also measured. Simple analysis of the experimental results, based on the Curie-Weiss law, reveals the way in which the spin value of Mn atoms and the exchange interaction between them depend on the crystal voluem (or lattice parameter).

Magnetic and crystallographic measurements on Fe 2.1- x Mn x As with 0≦ x ≦2.1 are made in the temperature range between 77 and 600 K. The compounds with 0≦ x

Thermal expansion of a ferromagnetic compound Mn 5 Ge 3 was determined from X-ray powder diffraction data at temperatures ranging from 100 to 400°K. From the thermal expansion curves, values of exchange striction along a and c axes were deduced. They are positive along the a axis and negative along the c axis respectively, and this fact leads to a weak dependence on pressure of the Curie temperature. Using the present data of the exchange striction, the pressure coefficient of the Curie temperature, (1/ T c ) (d T c /d p ), was estimated to be 14×10 -13 dyn -1 cm 2 , which agreed well with the directly measured values of 18×10 -13 dyn -1 cm 2 by the present writers and 15×10 -13 dyn -1 cm 2 by Block and Pauthnet.

Magnetic and crystallographic natures of compounds Mn 1- x Cr x As (0.3≧ x >0) were studied in the temperature ranges from 4.2° to 900°K and from 100° to 320°K. The compounds had MnP-type (B31) structure at low temperatures and transformed into NiAs-type (B8 1 ) structure at high temperatures. These compounds were metamagnetic at low temperatures. It was further confirmed that the deformation induced a low spin state of metal ions in the compounds, while with decease in deformation due to the rise of temperature, the metal ions in the compounds transfer to a high spin state, as in the case of MnAs 0.9 P 0.1 .

Crystallographic and magnetic properties of the compound MnAs 0.9 P 0.1 are studied in the temperature range from 4.2 to 660°K. X-ray diffraction studies reveal this compound deforms at 440°K with decreasing temperature from hexagonal B8 1 into orthorhombic B31 structure, as pointed out by Goodenough et al. . Degree of the orthorhombic deformation δ (shown in the text) in this case is first found to increase gradually from 440°K with lowering temperature, then rises steeply, reaching a δ-value of 2%, and remains constant with further fall of temperature. The magnetic measurements at low temperature reveal that the present compound is metamagnetic with saturation magnetization of 69 e.m.u. / g at 4.2°K, while it shows a ferromagnetic behavior above Liquid air temperature. Based on the present result, it can be shown that the manganese ion in this compound below Curie temperature is in a low spin state with spin value S =0.8. It is also shown that the manganese ions is in a high spin state for vanishing δ, ...

MnAlGe is a ferromagnet with a unique crystal structure including two‐dimensional arrays of Mn atoms in it. In order to find the magnetic properties characteristic of this structure, magnetic and electric measurements were made for Mn0.9M0.1AlGe (M:Mn, Cr, Fe) and MnGaGe. It has been found that the susceptibility above the Curie temperature (TC) does not obey the Curie–Weiss law over the very wide temperature range. Obtained susceptibility vs temperature curves are well expressed by a formula χg=C/(T−θa)γ with a composition dependent parameter γ ranging from about 1.3 to 1.5. In MnAlGe the formula with γ=1.49 holds in the whole temperature range from just above TC (=503 K) to Tt (=853 K, a temperature of solid‐state transition). The Curie temperature of Mn1−xMxAlGe(x≤0.2) varies monotonically when they are plotted against the averaged number of d electrons per transition‐metal atom. The temperature dependencies of saturation magnetization and electric resistivity were also measured for these specimens.

The temperature dependence of the lattice constants of CuCr 2 X 4 (X=S, Se and Te) was determined in a temperature range from 100 to 700 K by an X-ray diffraction technique. The specific heat of CuCr 2 Se 4 was also measured. The temperature dependence of the exchange strictions of CuCr 2 X 4 (X=S, Se and Te) was estimated from these results. Based on the molecular field theory proposed by Bean and Radbell, we estimated the pressure coefficients of the Curie temperature to be -1.1×10 -3 , -0.4×10 -3 and 0 deg. cm 2 /kg for CuCr 2 S 4 , CuCr 2 Se 4 and CuCr 2 Te 4 , respectively, which were in agreement with the values obtained by direct measurements.

Temperature dependence of lattice parameters of CrTe was measured in a temperature range from 113°K to 413°K, by the method of X-ray diffraction. Large expansion of the lattice was observed as temperature lowered through the Curie point (345°K). Exchange striction was obtained by subtracting normal thermal expansion due to lattice vibration from the observed thermal expansion curve. Temperature dependence of the exchange striction thus directly observed was shown to agree fairly well with that deduced, on the basis of the molecular field theory proposed by Bean and Rodbell, from results of the pressure effect of the Curie temperature and temperature dependence of saturation magnetization.

The effect of the pressure on the Curie temperature of CrTe and MnSb compounds of the nickel arsenide were studied up to a pressure of 4,000 kg/cm 2 . The rate of change of the Curie temperature was -5.5×10 -3 °C kg -1 cm 2 for CrTe and (-3.2±0.5)×10 -3 °C kg -1 cm 2 for MnSb. From the result of the present experiment, the critical pressure and temperature to realize a first kind transition from a ferromagnetic to a paramagnetic state in CrTe are evaluated to be 41,000 kg/cm 2 and 107°K, respectively.

Various types of structural phase transitions were found by means of X-ray techniques in the system CrAs1−xSbx (0⩽x⩽1). The magnetic measurements reveal that these transitions have a close relationship to the changes of the magnetic moment of Cr atom and/or the spin structure.

Magnetic measurements are carried out for Mn1−xMxAlGe (M=3d metals) alloys with x up to 0.2. A remarkable increase and decrease of the Curie temperatures with x are observed for M=Cr and Fe, respectively. The substitution of M with x less than 0.1 brings about the reduction in the averaged magnetic moment, which is especially large in the cases of Ti, Fe, and Co and of about 20% for x=0.1. From the measurement of Mossbauer spectrum at 77 K, the internal field at Fe atomic site is not found in Mn0.8Fe0.2AlGe. The reciprocal susceptibility versus temperature curves do not obey the Curie‐Weiss law and are concave upward for all the specimens. By adjusting the Curie‐Weiss law to the tangents of the highest parts of the χ−1g vs T curves, we obtain values of magnetic moments about 20 (for M=Mn) to 45% (for M=Fe) larger than those obtained from the saturation magnetizations.

The pressure effect of the Curie temperature of Mn 1− x Ti x As is studied with the magnetic properties and the thermal expansion. The sensitivity of the exchange interaction to the a axis is found to be about twenty times larger than that to the c axis. The sensitivity decreases with increasing x .

Magnetic susceptibilities have been measured for the mixed compounds Mn 1− x Cr x As (0≤ x ≤1) and the compound MnP in the temperature region up to 1400 K. The X 1 g vs. T curves of Mn 1− x Cr x As follow the Curie-Weiss law only in the temperature region where the crystal structure is of the B8 1 type. Some important problems are pointed out from the data.