Microwave absorption in high-Tc superconductors studied by the EPR method

Abstract

Dependences of the microwave absorption on temperature, magnetic field and microwave power obtained for the high-Tr superconductors are presented. Shape of the magnetically modulated microwave absorption, low-field phase diagram and overheating of the Josephson junction system induced by microwave irradiation are discussed. The model of the Josephson junction system interacting with microwaves has been used to explain the behavior of the high-T e superconductors in low magnetic field.

Microwave Absorption Study on (Bi, Pb)-Sr-Ca-Cu-O Granular Superconductors

“…The samples were annealed for the time intervals between 2 min and 20 h. The measurements of resistivity as a function of temperature are published elsewhere [3]. Magnetically modulated microwave absorption measurements were performed with a standard X-band EPR spectrometer RADIOPAN SE/X 2543 with TM 102 cavity and a 100 kHz magnetic field modulation B m [4]. The signals were recorded during a continuous change of temperature with the rate of 2 K/min.…”

Application of magnetically modulated microwave absorption to study of giant magnetoresistance effect in the Ni−Fe/Cu multilayer system

“…The output signal was proportional to the magnetic field derivative dPabs/dB of the absorbed microwave power Pabs" The differential response is due to the presence of another field modulated with a frequency fmod and detected by a lock-in amplifier. Magnetically modulated microwave absorption (MMMA), observed around a zero magnetic field, has been already successfully applied to Josephson-like dissipation in high-temperature superconductors [5]. In this paper, the MMMA method is applied for the Py/Cu system and it is shown to be a useful method to study the GMR effect and magnetization reversal in magnetic ML systems.…”

Lower Josephson critical field in granular HTS measured by microwave absorption

“…Lofland et al measured the values of Hcl J in a few YBa2Cu307 superconductors: these values ranged from a few tenths Oe to about 10 Oe. Now, the method of MMMA [9][10][11] should be especially applicable to measuring the Josephson critical fields. The reason is that microwave absorption in the range of lower magnetic fields is linked to the absorption of microwave energy by intragrain Josephson junctions [12][13][14].…”