Effect of substitution on the magnetic order in La₂(A_xNi_1-x)₇; A = Co, Cu

Small moment magnetic systems attract attention as their magnetic ordering temperatures can often be tuned towards a quantum phase transition, using non-thermal parameters, to study exotic physical phenomena such as unconventional superconductivity, heavy Fermi liquid, etc. Specific heat, electrical resistivity, and low field magnetization measurements indicate that in parent La₂Ni₇ there is a series of AFM phase transitions at 61.0K, 56.5K, and 42.2K with a low saturated moment of 0.12μ_B/Ni [1]. Tuning with hydrostatic pressure up to 2GPa indicated very little pressure dependence of the transition temperatures. We study the chemical substitution of Ni with its adjacent neighbors, Co and Cu, to create a different type of perturbation. Single crystals of La₂(A_xNi_1-x)₇; A = Co, Cu have been synthesized and characterized. Both the substituted systems show a change of the magnetic state with temperature and field based on the M(H,T) measurements. Composite T-H-x phase diagrams will be presented to follow the evolution of magnetic transitions in doped La₂Ni₇.

[1] Ribeiro, R. A. et al., Phys Rev B 105, 014412 (2022).