ESR Spectrometry of High-Temperature Superconductors with   Temperature-Modulation-Based Thermoregulation
  A light-beam-assisted temperature-control system operating within a temperature range from 77 to 180 K is developed for investigating the absorption of electromagnetic waves by high-temperature superconductors in the vicinity of superconducting transition with an ESR spectrometer. The advantage of this system is the feasibility of modulating the temperature of a sample with a frequency of 80 Hz and amplitude of 0.01 -0.1 K. The rms temperature instability over a 5-min time interval is within 0.06 K, the temperature gradient in a sample is 0.01 K/mm for T=90 K, and the system relaxation time is 1 - 10 s. The microwave absorption peaks in the vicinity of the superconducting transition of an Y-Ba-Cu-O, single crystal were first measured at (the simultaneous application of magnetic and temperature modulations. 
M.K. Aliev, G.R. Alimov, I.Kholbaev, T.M. Muminov, B. Olimov, B.Yu.   Sokolov and R.R. Usmanov (Institute of Applied Physics...