High Magnetic Field ESR in the Haldane Spin Chains NENP and NINO

TL;DR

This study investigates high magnetic field electron spin resonance in S=1 antiferromagnetic chains NENP and NINO, analyzing the quantum energy gap's field dependence with advanced numerical methods, considering anisotropy effects.

Contribution

Introduces the consideration of a staggered anisotropy term in analyzing ESR data in high magnetic fields for the first time.

Findings

Quantum energy gap varies with magnetic field B||b.

Spin dynamics are significantly affected by orthorhombic anisotropy E.

Numerical analysis aligns with experimental ESR measurements.

Abstract

We present electron spin resonance experiments in the one-dimensional antiferromagnetic S=1 spin chains NENP and NINO in pulsed magnetic fields up to 50T. The measured field dependence of the quantum energy gap for B||b is analyzed using the exact diagonalization method and the density matrix renormalization group method (DMRG). A staggered anisotropy term (-1)^i d(S_i^x S_i^z + S_i^z S_i^x) was considered for the first time in addition to a staggered field term (-1)^i S_i^x B_st. We show that the spin dynamics in high magnetic fields strongly depends on the orthorhombic anisotropy E.