Effects of Randomness on the Field-Induced Phase Transition in the S=1 Bond-Alternating Spin Chain NTENP

TL;DR

This study investigates how randomness affects the field-induced phase transition in an S=1 bond-alternating spin chain, revealing inhomogeneous magnetization and anisotropic antiferromagnetic behavior caused by disorder.

Contribution

It uncovers the effects of disorder on magnetic transitions in NTENP, highlighting the transformation from incoherent to coherent antiferromagnetic states due to randomness.

Findings

Inhomogeneous staggered magnetization observed at low temperatures.

Random anisotropic interactions caused by NO2 group disorder.

Anisotropic behavior of the field-induced antiferromagnetic transition.

Abstract

We report novel effects of randomness in the S=1 bond-alternating antiferromagnetic chain compound with a dimer-singlet ground state [Ni(N,N'-bis(3-aminopropyl)propane-1,3-diamine(mu-NO2]ClO4 abbreviated as NTENP. The 15N NMR spectra develop a continuum with sharply peaked edges at low temperatures, indicating an inhomogeneous staggered magnetization induced by magnetic field. We attribute this to random anisotropic interactions due to disorder of NO2 groups in the chains. The field-induced antiferromagnetic transition exhibits remarkably anisotropic behavior. We propose that a field-induced incoherent magnetization is transformed into a coherent antiferromagnetic moment with spatially fluctuating amplitude.