The spin-lattice relaxation rate 1/T1 and the Knight shift were measured for La1.85Sr0.15CuO4 and YBa2Cu4O8 under pressure to 1.4 GPa. The results together with the previously reported pressure dependence of the nuclear quadrupole frequency, νQ, give evidence that the local hole distribution changes under pressure. In La1.85Sr0.15CuO4, the hole density in the Cu 3d orbit decreases, accompanying a suppression of the antiferromagnetic spin fluctuation of the low-energy component. In YBa2Cu4O8, by contrast, the spin fluctuation changes little while the total hole number in the CuO2 plane increases. We argue that such changes in the hole distribution are responsible for the Tc increase in the respective compounds. We also found that the so-called "spin-gap" behavior in YBa2Cu4O8 becomes more pronounced under pressure.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering