# Reentrant Phase Diagram of $\rm{Yb_2Ti_2O_7}$ in $\langle 111 \rangle$ Magnetic Field

## TL;DR

This study maps the magnetic phase diagram of Yb2Ti2O7 in a <111> field, revealing an unusual reentrant phase boundary where small fields increase the ordering temperature, highlighting complex underlying interactions.

## Contribution

It provides the first detailed phase diagram of Yb2Ti2O7 in a <111> magnetic field, showing reentrant behavior and analyzing the limitations of classical models.

## Key findings

- Small magnetic fields increase the ordering temperature.
- Zero-field ground state has ferromagnetic domains.
- Classical Monte Carlo models partially explain the data but miss the reentrant bulge.

## Abstract

We present a magnetic phase diagram of rare-earth pyrochlore $\rm{Yb_2Ti_2O_7}$ in a $\langle 111 \rangle$ magnetic field. Using heat capacity, magnetization, and neutron scattering data, we show an unusual field-dependence of a first-order phase boundary, wherein a small applied field increases the ordering temperature. The zero-field ground state has ferromagnetic domains, while the spins polarize along $\langle 111 \rangle$ above 0.65T. A classical Monte Carlo analysis of published Hamiltonians does account for the critical field in the low T limit. However, this analysis fails to account for the large bulge in the reentrant phase diagram, suggesting that either long-range interactions or quantum fluctuations govern low field properties.