Journal of Magnetism and Magnetic Materials

We report on the successful single crystal growth of pure EuRh2Si2 and of Eu(Rh1−xCox)2Si2 with x≤0.23 by the flux method. Through Co substitution, EuRh2Si2 can be tuned from stable antiferromagnetism via a valence-transition state towards the valence-crossover regime. From magnetization measurements, we constructed a B−T phase diagram for EuRh2Si2 comprising multiple magnetic phases and showing a sizeable magnetic anisotropy within the basal plane of the tetragonal unit cell. This indicates a complex antiferromagnetic ground state for x=0. By applying positive chemical pressure through the substitution series Eu(Rh1−xCox)2Si2, a sharp temperature-induced first-order phase transition is observed in magnetization, resistivity and heat capacity for 0.081 ≤ x ≤ 0.126. The critical end point of this valence transition is located in the phase diagram in the vicinity of 0.126 <xEDX< 0.23. At higher substitution level, the system reaches a valence-crossover regime. The obtained results are presented in a temperature-substitution phase diagram. © 2025 The Authors