^{17}O and ^{51}V NMR for the zigzag spin-1 chain compound CaV2O4

TL;DR

This study uses ^{17}O and ^{51}V NMR techniques to investigate the magnetic properties of CaV2O4, revealing a long-range antiferromagnetic transition, multiple substructures, and an energy gap in the spin wave spectrum.

Contribution

It provides the first detailed NMR analysis of CaV2O4, identifying magnetic substructures and quantifying the energy gap in its antiferromagnetic excitations.

Findings

Long-range antiferromagnetic transition at ~78 K in powder and 69 K in crystals.

Presence of two collinear antiferromagnetic substructures with a 19° separation.

Energy gap in spin wave spectrum estimated between 64 and 98 K.

Abstract

$^{51}$V NMR studies on CaV2O4 single crystals and $^{17}$O NMR studies on $^{17}$O-enriched powder samples are reported. The temperature dependences of the $^{17}$O NMR line width and nuclear spin-lattice relaxation rate give strong evidence for a long-range antiferromagnetic transition at Tn = 78 K in the powder. Magnetic susceptibility measurements show that Tn = 69 K in the crystals. A zero-field $^{51}$V NMR signal was observed at low temperatures (f $\approx$ 237 MHz at 4.2 K) in the crystals. The field swept spectra with the field in different directions suggest the presence of two antiferromagnetic substructures. Each substructure is collinear, with the easy axes of the two substructures separated by an angle of 19(1) degree, and with their average direction pointing approximately along the b-axis of the crystal structure. The two spin substructures contain equal number of spins. The temperature dependence of the ordered moment, measured up to 45 K, shows the presence of an energy gap Eg in the antiferromagnetic spin wave excitation spectrum. Antiferromagnetic spin wave theory suggests that Eg lies between 64 and 98 K.