Electron spin resonance in single crystal YBa₂Cu₃0_7-δ and EuBa₂Cu₃0_7-δ

Abstract

We have observed, in good single crystals of YBa₂Cu₃0_7-δ, a strong paramagnetic resonance signal characteristic of Cu²⁺ ions in the | x² − y² > state. We observe this signal in both the 40K phase and in the high-T_c ∼ 90K phase. The signal intensity is enhanced at low temperatures, though no anomaly is seen at other temperatures. the signal is broad, with peak to peak width of 0.025 T. Our signal crystals of EuBa₂Cu₃0_7-δ however, show a resonance that is similar to a Y₂BaCu0₅ phase. This signal intensity is enhanced ∼ 3 times at 77K. There was no significant change in the linewidth with temperature.