Avoided Quantum Critical Point in La₅(Co_1-xNi_x)₂Ge₃

La₅Co₂Ge₃ is an itinerant ferromagnetic system that undergoes a second order phase transition at 3.8K with a low-field saturated moment of about 0.1 μ_B/Co¹, making it a promising candidate for tuning the transition to even lower temperatures with a non-thermal tuning parameter like pressure, chemical substitution, or magnetic field. Under applied pressure, the FM transition in La₅Co₂Ge₃ is weakly suppressed to 3 K at 1.7 GPa, upon which a new possibly magnetic, phase emerges upto 5.12GPa². The new phase is presumed to be antiferromagnetic, meaning the FM QCP appears to be avoided in favor of an AFM ground state. Here we further study the La₅Co₂Ge₃ system using Ni substitution. We synthesize single crystals of La₅(Co_1-xNi_x)₂Ge₃ with x = 0.01–0.10 and construct a T-x phase diagram from magnetization, transport, and thermodynamic measurements. Details of this diagram will be discussed and compared to the earlier T-P work.

1.           Saunders, S. M. et al., Phys Rev B 101, (2020).

2.           Xiang, L. et al., Phys Rev B 103, (2021).