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The GL coherence lengths were evaluated to be 21±1 and 13±1 A for K3C60 and Rb3C60, respectively, by magnetization measurements based upon the renormalization theory of the fluctuation.

The Ginzburg-Landau coherence lengths were evaluated for C 60 -based superconductors by fitting measured magnetization data with the renormalization theory of the fluctuation. The derived coherence lengths are 21±1 and 13±1 A for K 3 C 60 and Rb 3 C 60 , respectively, which are preliminary results but are apparently smaller than the reported values obtained from H c2 (0) with mean field theory.

A magnon sideband which has an anomalous shape with the cut-offs at the low as well as the high energy sides was observed in the lowest energy region of the absorption spectra 6 A 1g → 4 T 2g ( 4 D ) in (C 2 H 5 NH 3 ) 2 MnCl 4 . This band shape is well fitted by the calculation of the shape of magnon sideband, considering both the inter- and intra-sublattice exciton transfers. The magnitudes of the inter- and intra-sublattice exciton transfers are estimated to be 10.2 cm -1 and 6.8 cm -1 , respectively, from the analysis of the band shape. The behaviour of this magnon sideband in the magnetic field was measured at 4.2 K. From its behaviour, the spin flop field is estimated to be 30±5 kOe, which is confirmed by the measurement of magnetization. The existence of exciton dispersions is supported by the effects of magnetic field and uniaxial stress on this magnon sideband.

The dependence of the absorption spectra of CsCoCl 3 on temperature and a magnetic field was investigated. It was found that the energy difference between the exciton line and its hot sideband is nearly equal to the soliton energy, and the intensity of the hot band is proportional to the thermal probability of the soliton below T N1 . Therefore, it was concluded that the hot band is ascribed to the exciton creation at the thermally excited soliton.

The crystal field absorption spectra in the near infrared to visible regions of CsCoCl 3 ·2H 2 O were investigated. All of the absorption bands were well assiged by taking the crystal field and Racah parameters as D q =720 cm -1 , B =920 cm -1 and C =4320 cm -1 , respectively. In the spin forbidden transition 4 T 1 ( 4 F )→ 2 T 1 ( 2 P ) the exciton line and its magnon sideband were observed. The one-dimensionality of magnetic properties is reflected in the temperature dependence of the peak energy and the integrated intensity of the magnon sideband.

Zeeman effect of the R and B lines in GCrSH was measured. No difference was observed between the Zeeman patterns of the R 1 and R 2 absorption lines. Non-zero g -values of the excited states were obtained from the patterns in a magnetic field perpendicular to the trigonal axis. From these results, it is concluded that these two lines are not attributed to the two transitions 4 A 2 →\bar E ( 2 E ) and 4 A 2 →2\bar A ( 2 E ) of a Cr 3+ ion, but to the transition 4 A 2 →\bar E ( 2 E ) in the two different Cr 3+ sites. Both the B 1 and the B 1 ' lines were assigned to 4 A 2 →\bar E b ( 2 T 2 ) from the Zeeman patterns in a high pulsed magnetic field. New lines were found in the R -line region when GCrSH was diluted by aluminum. They are considered to originate from certain kinds of Cr 3+ sites and to have relation with the ferroelectric character of the crystals. In the B -line region, however, no new lines were observed.

The Zeeman effect of a sharp line in the red region of cesium chromium alum was investigated at low temperatures, using the magnetic fields up to 27 kOe, which were applied parallel to the [100], [111], and [110] axes. The g values and the quantization axis of the excited state of a Cr 3+ ion were determined. Comparing the experimental Zeeman patterns with the theoretical ones on the basis of the ligand field theory, it is concluded that the absorption line corresponds to the magnetic dipole transition from the ground state 4 A 2 to the excited state \bar E ( 2 E ). Although the transition from the ground state 4 A 2 to the excited state 2\bar A ( 2 E ) is not observed, it is suggested that the energy separation between the two states 2\bar A ( 2 E ) and \bar E ( 2 E ) is much larger than 3.5 cm -1 .

The absorption spectra 6 A 1g → 4 T 2g ( 4 D ) of Mn +2 in the layer type antiferromagnet (C 2 H 5 NH 3 ) 2 MnCl 4 were measured. An absorption band caused by electric dipole was observed, which has an anomalous shape with cut-offs at the low as well as the high energy sides. The temperature dependence of its intensity suggests that it is a magnon sideband. The anomalous shape of this band could be reproduced in calculation as magnon sideband, taking account of the magnon dispersion and the exciton dispersion due to inter- and intra-sublattice transfers. Measurements of the uniaxial stress effect were also undertaken to investigate details of the behaviours of this magnon sideband.

Optical absorption spectra corresponding to the 6A1g→4T2g(D) transition in CSMnCl3⋅2H2O and (CH3)2NH2MnCl3⋅2H2O were investigated under magnetic fields. In these compounds, a sharp exciton line in the lowest energy region of this transition was split by the applied field perpendicular to the spin direction. From the analysis of the spin configuration, it was proved to be a Davydov splitting induced by the field. The field induced Davydov splitting can be explained by the fact that in an external magnetic field perpendicular to the spin direction, spins cant towards the field so as to remove the prohibition of the inter-sublattice exciton transfer. The field dependence of this splitting was explained by the exciton transfer due to the anisotropic exchange interaction.

The absorption spectra corresponding to the transition 4T1 (4F)→2T1(2P) of Co2+ in CSCoCl32H2O were investigated under high magnetic fields up to 230kOe with a hybrid magnet. The anomalous line shapes of the magnon sideband with a double peak were observed under the magnetic fields parallel to the a- and c-axes. The behavior of the magnon sideband under the external magnetic fields is related to the exciton transfer. The intrachain exciton transfer becomes large under the magnetic field that induces the ferromagnetic components of the spins. This change of the exciton dispersion is reflected in the line shape of the magnon sideband. The anomalous behavior of the magnon sideband under the external fields was elucidated by the calculation of the line shape taking into account the field dependence of the exciton transfer.

The absorption spectra in one-dimensional antiferromagnet CsFeCl3⋅2H2O were investigated. From the dependence on uniaxial stress and temperature, the absorption lines observed in the region of 24150 - 24350cm-1 were assigned as exciton lines or magnon sidebands. The one-dimensionality of magnetic properties is reflected in the temperature dependence of exciton lines and magnon sidebands. Under the external magnetic field, the sublattice splitting and the Davydov splitting of the exciton lines were observed.

Magneto-absorption spectra of one dimensional antiferramagnet CsFeCl3⋅2H2O have been measured in the energy region of 24150 - 24350 cm-1 at 4.2 K under the steady magnetic field up to 220 kOe using a hybrid magnet system. The sublattice splitting of the exciton and magnon sideband lines was observed up to 140 kOe, where the metamagnetic transition from antiferramagnetic to ferramagnetic state takes place when the magnetic field is applied parallel to the chain 'along the a-axis. Discontinuous changes of the spectra were found in absorption lines of the exciton and magnon sideband at the transition field.