Operation of Magnets in High Field Laboratory for Superconducting Materials of IMR

This paper serves as a preface to the present special issue of Sci. Rep. RITU, describing the brief history and the present status of High Field Laboratory for Superconducting Materials (HFLSM), which reached the 10th anniversary last year. The HFLSM is equipped with steady-high-field magnets such as superconducting magnets, high-power water-cooled magnets and hybrid magnets. The facilities have been used for a variety of cooperative research programs. Some significant achievements in researches on superconducting materials appear in this issue, and another issue concerning various high-field researches will be published soon

Magneto-optical Measurements using a Hybrid Magnet(Part II. Several Instruments and Techniques Developed in HFLSM)

Magneto-absorption spectra were obtained in the fields up to 23 T by means of a hybrid magnet at Tohoku University. The absorption was obtained by measuring the intensity of transmitted light through the sample. Optical fiber systems were utilized for the light transmission, which enabled rapid assembly of the light pass within a restricted machine time. The spectra were taken in the wavelength region of about 300 to 2000 nm. The monochromator was fully remote controlled from outside of the magnet room by a computer

Magnetization and AC-Susceptibility of Fe-Zr Amorphous Alloys

Measurements of magnetization and ac-susceptibility of Fe-Zr amorphous alloys over the wide composition range have been carried out. The spin glass like behavior appears in two different regions of composition. The spin glass behavior in Fe-rich Fe amorphous alloys (around 90 at.% Zr) is due to the frustration of antiferromagnetic coupling between spins. The other behavior around 50 at.% is due to the dilution of atoms with magnetic moment. They are explained by the local environment effect

Magneto-Absorption Spectra of One-Dimensional Ising Antiferromagnets in High Magnetic Fields(Magnetooptics)

We have performed magneto-absorption spectra measurements of the quasi-one-dimensional antiferromagnet RbFeCl_3.2H_2O with a hybrid magnet installed at High Field Laboratory for Superconducting Materials in Tohoku University

Production of Ultrahigh Magnetic Fields by Explosive-Driven Flux Compression

Magnetic fields exceeding 1 MOe are reproducibly generated by a flux compression method using a cylindrical metal liner and high explosives. Some new devices are employed for simultaneous initiation of the cylindrical explosive on its outer surface. Detailed measurements are made on the dependence of the liner velocity on the mass ratio of liner and explosive. The results are consistent with an analysis based on the theory of detonation

Magnetization Curves of the Reentrant-Spin-Glass Fe_<0.65>Mn_<0.35>TiO_3 : Dependence on the Sweep Rate of Magnetic Fields(Magnetism)

The magnetization curves of the reentrant-spin-glass Fe_Mn_TiO_3 have been observed at 4.2 K and 1.4 K in applied fields with various sweep rates. Depending on the sweep rates and temperatures, the anomalous jumps of the magnetizations towards the values of the field-cooled-magnetization M^ are observed. This phenomenon is interpreted to be closely related to the properties of the spin-glass state

High-Sensitivity Streak Camera Applicable to Time-Resolved Spectroscopy

A high-sensitivity streak camera has been designed and manufactured using a photoelectric tube with deflecting plates and a microchannel plate which serves as both a streak device and an image intensifier. Characteristics of the complete equipments are as follows : (1) an image on the film is 10.2 times as large as an image on the photoelectric surface, (2) effective area of the film is 45 mm in diameter, (3) resolution on the film is 2.5 lp/mm (4) writing speed on the film is 0.2～20 mm/μs, 5-stage variable, (5) sensitivity is controlled by the microchannel plate voltage, and (6) a spectroscope is combined to take time-resolved spectrographs, 1 mm on the film corresponding to 0.9 nm of the wavelength

High Field Magnetization in Manganese Intermetallic Compounds(Magnetism)

Magnetization measurements were carried out on manganese intermetallic compounds Mn_3MC(M=Ga, Zn), Mn_Co_xSb(x=0.09 and 0.15) and MnMX(M=Ru, Rh, Pd;X=As, P)in magnetic fields up to 150 or 320 kOe. Antiferromagnetic(AF)-ferromagnetic(F) field-induced transitions and (AF+F)-(F) one were observed for Mn_3GaC and Mn_3ZnC, respectively. For Mn_Co_Sb, intermediate(I)- ferrimagnetic(Fr) field-induced transitions were observed. For Mn_Co_Sb, AF-Fr field-induced transitions were observed. These transitions were of the first order except one of Mn_3ZnC. The magnetic properties of MnMX (M=Ru, Rh, Pd;X=As, P) were discussed on the basis of the values of magnetization and high-field magnetic susceptibility

Shock Compression Experiments in Solids using High Explosives

Small-scale explosive plane wave generators, 40-78 mm in diameter, are developed to perform solid state experiments at shock pressures up to 1 Mbar. Techniques for determining the shock compression curve are described in detail, especially in the case where a phase transformation occurs at a high pressure

SPEROMAGNETISM IN HOMOGENEOUS OXIDE GLASSES CONTAINING A LARGE AMOUNT OF Fe^<3+> IONS

Structural and magnetic properties of homogeneous oxide glasses containing a large amount of Fe^ ions, are reviewed. A comparative study of the glass and its corresponding crystal, mostly by Mossbauer spectroscopy, reveals that short-range atomic arrangements in the glass do not show much difference from that of the crystal, as far as a few interatomic distances are concerned. The magnetic state in the glasses is characterized by a narrow distribution and a Brillouin-function-like temperature dependence of the internal field, a rather sharply defined magnetic ordering temperature, and remarkable thermoremanence induced in the field-cooling experiments. Surprisingly large reduction in the magnetic ordering temperature of the glass is to be noted, when compared with the coresponding crystal. These observations are consistently interpreted by the concept of spero-magnetism proposed by Coey, where short-range antiferromagnetic order prevails only for a few atomic distances. It is pointed out that the Fe^ ion is particularly favorable species as a network former in the homogeneous glasses because of its (3d)^5 configuration, being insensitive to crystal field effect