NMR characterization of spin-1/2 alternating antiferromagnetic chains in the high-pressure phase of (VO)2P2O7

Local-susceptibility measurements via the NMR shifts of ${}^{31}$P and ${}^{51}$V nuclei in the high-pressure phase of (VO)${}_2$P${}_2$O${}_7$ confirmed the existence of a unique alternating antiferromagnetic chain with a zero-field spin gap of 34 K. The ${}^{31}$P nuclear spin-lattice relaxation rate scales with the uniform spin susceptibility below about 15 K which shows that the temperature dependence of both the static and dynamical spin susceptibilities becomes identical at temperatures not far below the spin-gap energy.