Spin-Peierls transition in TiPO$_4$

TL;DR

This study explores the magnetic and structural phase transitions in TiPO₄, revealing a spin-Peierls transition at 74 K characterized by bond alternation and incommensurate phases, using multiple experimental and computational methods.

Contribution

It provides the first detailed investigation of the spin-Peierls transition in TiPO₄, combining experimental data and density functional theory to elucidate the phase transition mechanism.

Findings

TiPO₄ exhibits two magnetostructural phase transitions at 111 K and 74 K.

Below 74 K, TiPO₄ shows a spin-Peierls transition with bond alternation.

An incommensurate phase exists between 111 K and 74 K.

Abstract

We investigated the magnetic and structural properties of the quasi-one dimensional 3$d^1$-quantum chain system TiPO$_4$ ($J \sim$ 965 K) by magnetic susceptibility, heat capacity, ESR, x-ray diffraction, NMR measurements, and by density functional calculations. TiPO$_4$ undergoes two magnetostructural phase transitions, one at 111 K and the other at 74 K. Below 74 K, NMR detects two different $^{31}$P signals and the magnetic susceptibility vanishes, while DFT calculations evidence a bond alternation of the Ti...Ti distances within each chain. Thus, the 74 K phase transition is a spin-Peierls transition which evolves from an incommensurate phase existing between 111 K and 74 K.