The non-resonant microwave absorption (NRMA) measurements have been intensively performed for superconducting thin films of YBa 2 Cu 3 O y fabricated on MgO (100) substrates and powder samples of LaSrCuO systems. In order to complement the study, we also review the NRMA of BiSrCaCuO system. A particular attention has been paid to the following phenomena: (i) phases, (ii) effect of current, (iii) directional effect of applied magnetic field, (iv) hysteresis, (v) microwave power absorbed as a function of magnetic field, (vi) linewidth in the vicinity of T c , and (vii) modulation amplitude effect. A preliminary study on ( La 0.98 Dy 0.02)1.85 Sr 0.15 CuO 4 was also reported.

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We investigate full dynamical behaviors of the spin-Peierls transition in Sϭ1/2 Heisenberg antiferromagnetic chains by means of two-time Green's functions. The effect of temperature-dependent lattice displacements is incorporated self-consistently. Depending on temperature T and transfer wave number k, the imaginary part of the dynamical susceptibility zz Љ (k,) shows rich structures: At Tϭ0, it is nonvanishing in the frequency region ⍀ M (k)Ͻ⍀ (ϵប/J)Ͻ⍀ H (k). ⍀ M (k) denotes a lower edge of a triplet magnetic excitation continuum, and is finite at kϭ0 due to lattice distortion. The upper edge ⍀ H (k) increases as kϭ0 is approached, which is completely different from the feature without lattice distortion. An asymmetric line shape of zz Љ (k,) is found with a peak at the frequency slightly higher than ⍀ M (k). At 0ϽTϽT SP ͑spin-Peierls transition point͒ there appears another structure due to thermal fluctuations in the lower-frequency region, 0 Ͻ⍀Ͻ⍀ L (k). Since ⍀ L (k)Ͻ⍀ M (k), the forbidden band always exists at TϽT SP . Above T SP , zz Љ (k,) reduces to a smooth curve characterized by a single broad maximum. These features in dynamics are systematically explained in terms of different quasiparticle scattering processes proper to the spin-Peierls phase. The results are compared with recent experimental data of neutron scattering for the inorganic compound CuGeO 3 .

ESR measurements have been carried out on La 0.7 Ca 0.3 MnO 3. Distorted signals have been observed below about 255 K, but clear signals above ≃ 270 K . The temperature dependence of the low-temperature ESR linewidth nearly follows the magnetization (or susceptibility). The ESR intensity exhibits an anomalous increase at temperatures between about 200 K and 260 K with a peak at around 250 K; quite similar behavior to that of the resistivity, indicating a possible correlation between the resistivity and the ESR intensity. The temperature dependence of the ESR linewidth and intensity has been also studied above 300 K.

ESR measurements have been carried out for La 0.97 Ca 0.03 MnO 3 at temperatures from 4 K up to 760 K. below ≃243 K , two kinds of spectra, the high-field and low-field signals, are observed down to 96 and 4 K, respectively. They are assumed to be due to Mn 4+ and Mn 3+ ions, respectively. From the g-shifts of the high-field ( Mn 4+) signals, the magnetic interaction coefficient between Mn 4+ and Mn 3+ spins is estimated. Clear single ESR was observed above ≃255 K , and its linewidth and intensity are obtained as a function of temperature. The linewidth nearly follows exp (-550/T), and the intensity gradually deviates from Curie's law below ≃550 K , presumably due to the spin-cluster formation.