Magnetic field dependence of the antiferromagnetic phase transitions in Co-doped YbRh_2Si_2

TL;DR

This study investigates how magnetic field influences antiferromagnetic phase transitions in Co-doped YbRh2Si2, revealing complex phase behavior and the effects of doping on transition temperatures and transition types.

Contribution

First specific-heat measurements of Yb(Rh_{1-x}Co_x)_2Si_2 at various Co contents, uncovering complex magnetic phase diagrams and the impact of magnetic field on phase transitions.

Findings

Co-doping stabilizes magnetic phases due to unit cell volume decrease.

Transition from two mean-field-like to one sharp transition with increasing Co content.

Magnetic field suppresses magnetic phase transitions, with no evidence of field-induced first-order transition.

Abstract

We present first specific-heat data of the alloy Yb(Rh_(1-x)Co_x)_2Si_2 at intermediate Co-contents x=0.18, 0.27, and 0.68. The results already point to a complex magnetic phase diagram as a function of composition. Co-doping of YbRh_2Si_2 (T_N^{x=0}=72 mK) stabilizes the magnetic phase due to the volume decrease of the crystallographic unit cell. The magnetic phase transitions are clearly visible as pronounced anomalies in C^{4f}(T)/T and can be suppressed by applying a magnetic field. Going from x=0.18 to x=0.27 we observe a change from two mean-field (MF) like magnetic transitions at T_N^{0.18}=1.1 K and T_L^{0.18}=0.65 K to one sharp \lambda-type transition at T_N^{0.27}=1.3 K. Preliminary measurements under magnetic field do not confirm the field-induced first-order transition suggested in the literature. For x=0.68 we find two transitions at T_N^{0.68}=1.14 K and T_L^{0.68}=1.06 K.