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We have performed 59 Co spin-echo NMR measurements on Ce n +1 Co 3 n +5 B 2 n ( n = 0, 1, 2, 3) at T= 1.4 K. The NMR spectra corresponding to the inequivalent crystallographic sites were obtained. The resonance frequencies of the 2c-Co have been observed in the range 60-80 MHz, and those of the 6i-Co(6i 1 -Co) around 32 MHz. In addition to the zero-field spectra, the field-swept spectra from non-magnetic Co have also been observed for Ce 3 Co 11 B 4 and Ce 2 Co 7 B 3 . These spectra arise from the 3g-Co in Ce 3 Co 11 B 4 and the 6i 2 -Co in Ce 2 Co 7 B 3 . From the Co hyperfine field analysis, the Co magnetic moments at the inequivalent crystallographic sites are estimated. Magnitude of the spin moment for the 2c-Co is estimated to be μ B for Ce n +1 Co 3 n +5 B 2 n (n = 0, 1, 2, 3), and to be about 0.4 μ B for the 6i 1 -Co in Ce 3 Co 11 B 4 and Ce 2 Co 7 B 3 , while the orbital moment of the 2c-Co varies from μ B in CeCo 5 to μ B in Ce 2 Co 7 B 3 , and those for the 3g-Co and 6i 1 -Co are found to be 0.08 and 0.01 μ B , respectively. The Co magnetic moments are found to be strongly influenced by the crystallographic environment around the Co site.

A preliminary experiment for producing narrow-photon-energy cone-beam X-rays using a silicon single crystal is described. In order to produce low-photon-energy X-rays, a 100-μm-focus X-ray generator in conjunction with a (1 1 1) plane silicon crystal is employed. The X-ray generator consists of a main controller and a unit with a high-voltage circuit and a microfocus X-ray tube. The maximum tube voltage and current were 35 kV and 0.50 mA, respectively, and the X-ray intensity of the microfocus generator was 48.3 μGy/s at 1.0 m from the source with a tube voltage of 30 kV and a current of 0.50 mA. The effective photon energy is determined by Bragg's angle, and the photon-energy width is regulated by the angle delta. Using this generator in conjunction with a computed radiography system, quasi-monochromatic radiography was performed using a cone beam with an effective energy of approximately 17 keV.

The tungsten plasma flash X-ray generator is useful in order to perform high-speed enhanced K-edge angiography using cone beams because K-series characteristic X-rays from the tungsten target are absorbed effectively by gadolinium-based contrast media. In the flash X-ray generator, a 150 nF condenser is charged up to 80 kV by a power supply, and flash X-rays are produced by the discharging. The X-ray tube is a demountable diode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Since the electric circuit of the high-voltage pulse generator employs a cable transmission line, the high-voltage pulse generator produces twice the potential of the condenser charging voltage. At a charging voltage of 80 kV, the estimated maximum tube voltage and current were approximately 160 kV and 40 kA, respectively. When the charging voltage was increased, the characteristic X-ray intensities of tungsten K α lines increased. The K α lines were clean, and hardly any bremsstrahlung rays were detected. The X-ray pulse widths were approximately 110 ns, and the time-integrated X-ray intensity had a value of approximately 0.35 mGy at 1.0 m from the X-ray source with a charging voltage of 80 kV. Angiography was performed using a film-less computed radiography (CR) system and gadolinium-based contrast media. In angiography of non-living animals, we observed fine blood vessels of approximately 100 μm with high contrasts.

In the plasma flash X-ray generator, a 200 nF condenser is charged up to 50 kV by a power supply, and flash X-rays are produced by the discharging. The X-ray tube is a demountable triode with a trigger electrode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Target evaporation leads to the formation of weakly ionized linear plasma, consisting of nickel ions and electrons, around the fine target, and intense K α lines are left using a 15-μm-thick cobalt filter. At a charging voltage of 50 kV, the maximum tube voltage was almost equal to the charging voltage of the main condenser, and the peak current was about 18 kA. The K-series characteristic X-rays were clean and intense, and higher harmonic X-rays were observed. The X-ray pulse widths were approximately 300 ns, and the time-integrated X-ray intensity had a value of approximately 1.0 mGy at 1.0 m from the X-ray source with a charging voltage of 50 kV.

In the plasma flash X-ray generator, a high-voltage main condenser of approximately 200 nF is charged up to 50 kV by a power supply, and electric charges in the condenser are discharged to an X-ray tube after triggering the cathode electrode. Flash X-rays are then produced. The X-ray tube is a demountable triode connected to a turbo molecular pump with a pressure of approximately 1 mPa. As electrons from the cathode electrode are roughly focused onto a rod nickel target of 3.0 mm in diameter by the electric field in the X-ray tube, a weakly ionized linear plasma consisting of nickel ions and electrons forms by target evaporation. At a charging voltage of 50 kV, the maximum tube voltage was almost equal to the charging voltage of the main condenser, and the peak current was about 17 kA. When the charging voltage was increased, the linear plasma formed, and the intensities of K-series characteristic X-rays increased. The K-series lines were quite sharp and intense, and hardly any bremsstrahlung rays were detected. The X-ray pulse widths were approximately 700 ns, and the time-integrated X-ray intensity had a value of approximately 30 μC/kg at 1.0 m from the X-ray source at a charging voltage of 50 kV.

The development of a portable X-ray generator with a cerium-target tube and its application to angiography are described. The portable X-ray generator consists of a main controller, a unit with a Cock–Croft circuit and an X-ray tube, and a personal computer. Negative high voltages are applied to the cathode electrode in the X-ray tube, and the tube voltage and current are regulated by the controller or the computer. The X-ray tube is a glass-enclosed double-focus diode with a cerium target and a 0.5 mm-thick beryllium window. The maximum tube voltage and current were 60 kV and 0.8 mA, respectively. The focal-spot sizes were 4 mm ×4 mm (large) and 1 mm ×1 mm (small), respectively. Angiography was performed with a computed radiography system using iodine-based microspheres. The tube voltage, the current, the distance between the imaging plate and the X-ray source, and the spot size were 60 kV, 0.4 mA, 1.5 m, and small, respectively. In this angiography, we observed coronary arteries and fine blood vessels of about 50 μm or less with high contrasts.

A fundamental study on quasi-monochromatic parallel radiography using a polycapillary plate and a copper-target X-ray tube is described. The X-ray generator consists of a negative high-voltage power supply, a filament (hot cathode) power supply, and an X-ray tube. The negative high-voltage is applied to the cathode electrode, and the anode electrode is connected to the ground. In this experiment, the tube voltage was regulated from12–25 kV, and the tube current was regulated within 3.0 mA by the filament temperature. The exposure time was controlled in order to obtain optimum X-ray intensity, and the maximum focal spot dimensions were approximately 2 mm ×1.5 mm. The polycapillary plate was J5022-21 (Hamamatsu Photonics Inc.), and the plate thickness was 1.0 mm. The outer, effective, and hole diameters were 87 mm, 77 mm, and 25 μm, respectively. Quasi-monochromatic X-rays were produced using a 10 μm-thick copper filter, and these rays were formed into parallel beams by the polycapillary, and the radiogram was taken using a computed radiography system utilizing imaging plates. In the measurement of image resolution, the resolution fell according to increases in the distance between the chart and imaging plate using a polycapillary. We could observe a 50 μm tungsten wire clearly, and fine blood vessels of approximately 100 μm were visible in angiography.

X-ray absorption and magnetic circular dichroism measurements were carried out around the Sm M 4 , 5 and Co L 2 , 3 edges on SmCo 3 B 2 . The valence of Sm ions in SmCo 3 B 2 is trivalent. Co-3d electrons of SmCo 3 B 2 are more localized than those of pure Co metal and SmCo 5 . The component of the orbital magnetic moment of Co-3d electrons in SmCo 3 B 2 enhances in comparison with that of pure Co metal.

Electronic structures of YCo 4 B and YCo 3 B 2 are calculated in a self-consistent linear muffin-tin orbital method and the atomic sphere approximation. The effects of B atom in these compounds are discussed, by comparing the calculated local density-of-states curves with those of YCo 5 obtained previously. A good agreement between the calculated and observed values of the low-temperature specific heat coefficient for YCo 3 B 2 is obtained. Spin-polarized band calculations are also carried out and the local spin and orbital magnetic moments are evaluated at each Co atom site in YCo 4 B. It is found that the Co moment on 6i site is small, while the Co moment on 2c site is large. On the other hand, YCo 3 B 2 is found to be non-magnetic. These results are consistent with the observed ones and can be explained by the mixing model between 3d-states of Co and 2p-states of B.

The magnetic and crystallographic properties of MnAs0.75P0.25 compound have been measured in a wide temperature range. It has been found that the temperature-induced magnetic transition (1.4μB/Mn → 3.4μB/Mn) takes place corresponding to the structural transition (B31 → B8t) in this compound. Both the magnetic and structural transitions seem to take place in the narrow temperature region of 477 K

Magnetic properties of the compounds CrX with X Sb, As and P are known to change significantly as X changes from Sb to P. In order to discuss the relation between the magnetic properties and the crystal structures in CrX compound system, electronic structures have been calculated by the full potential linear muffin-tin orbital method. It is pointed out that the Cr3d orbitals in the c -plane in CrX compounds probably play an important role for the significant change of magnetic properties as X changes from Sb to P. Paramagnetic CrP and collinear antiferromagnetic CrSb with Cr-moment of about 3.0 μ B have also been explained by the present calculations.

Magnetic properties of a series of compounds Ce n +1 Co 3 n +5 B 2 n with n =1, 2, 3, and ∞ have been studied. Magnetic moments of Co atoms occupying different crystallographic sites have been separately estimated on the basis of the observed saturation magnetizations and some assumptions. Neutron diffraction measurements have also been carried out on the compounds shown in the title, and have revealed that magnetic moments of the Co atoms at 2c-, 6i-, and 3g-sites and the Ce atom in Ce 3 Co 11 B 4 are 1.4, 0.4, 0, and −0.1 μ B (Bohr magneton), respectively. The data thus obtained are compared with those of Y n +1 Co 3 n +5 B 2 n .

Magnetic and crystallographic properties have been observed for the compounds Ce 2 (Co 1− x Fe x ) 7 B 3 with x from 0 to 0.28. Metamagnetic properties of Ce 2 Co 7 B 3 transform to ferromagnetic characteristics by Fe substitution for the Co. It is revealed that the Fe atoms in the compounds substitute preferentially the Co atoms at the 2c-site. Magnetic moments of Fe atoms at the 2c- and 6i 1 -sites are estimated to be 2.8 μ B (Bohr magneton) and 0.35 μ B , respectively. Novel magnetic structure is proposed for the compounds Ce 2 (Co 1− x Fe x ) 7 B 3 .

Magnetic measurements have been made for the compounds Sm(Co 1− x Ni x ) 3 B 2 with x from 0 to 0.3. Temperature dependences of lattice parameters of SmCo 3 B 2 have also been measured between T =10 and 300 K. On the basis of the present data, magnetic moment of Sm and the induced moment of Co in SmCo 3 B 2 have been determined to be 0.13 μ B (Bohr magneton) and 0.017 μ B , respectively. The very small Sm-moment is explained by the huge crystal field effects. Magnetic transition at T =43 K and the high Neel temperature are also briefly discussed.

Electronic and magnetic states of CeCo 5− x B x are studied element-specifically by means of high-resolution bulk-sensitive resonant photoemission spectroscopy (RPES) and soft X-ray absorption magnetic circular dichroism (MCD). Judging from MCD of the ferromagnetic CeCo 5 , the spins of Ce 4f and Co 3d electrons couple antiferromagnetically with each other. RPES spectra show that the Ce 4f states are itinerant and form strongly mixed bands with the Co 3d states.

59 Co NMR spectra have been measured in RCo 3 B 2 (R = Y, Sm) under external magnetic field up to 1.8 T at 4.2 K. The 59 Co hyperfine fields are estimated as zero and -0.11 T for YCo 3 B 2 and SmCo 3 B 2 , respectively. The Co magnetic moments induced by the spin of R ion are discussed.

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.

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.

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.