Field-induced incommensurate phase in the strong-rung spin ladder with ferromagnetic legs

TL;DR

This study investigates a strong-rung S=1/2 Heisenberg spin ladder with ferromagnetic legs, revealing a field-induced incommensurate phase and frustration effects through magnetization, specific heat, and NMR measurements.

Contribution

It provides the first detailed experimental evidence of a field-induced incommensurate phase in a ferromagnetic-leg spin ladder, highlighting frustration effects.

Findings

Discovery of a field-induced successive phase transition.

Observation of incommensurate long-range order.

Evidence of magnetic frustration due to weak interladder couplings.

Abstract

We report magnetization, specific heat, and NMR measurements of 3-Br-4-F-V [=3-(3-bromo-4-fluorophenyl)-1,5-diphenylverdazyl], a strong-rung S=1/2 Heisenberg spin ladder with ferromagnetic leg interactions. We explain the magnetic and thermodynamic properties based on the strong-rung regime. Furthermore, we find a field-induced successive phase transition in the specific heat and the nuclear spin-lattice relaxation rate 1/T1. 19F-NMR spectra for higher- and lower-temperature phases indicate partial magnetic order and incommensurate long-range order, respectively, evidencing the presence of frustration due to weak interladder couplings.