Magnetic phase diagram of Ce (Mn1-x Cux)2 Si2

The magnetic structure of mixed valence-Kondo-heavy fermion series Ce (Mn1-x Cux)2 Si2 (0≤x≤1) is reported. The magnetic susceptibility results indicate that for 0≤x≤0.3, Mn moments are antiferromagnetically (AFM) ordered and the Neel temperature TN decreases rapidly with decreasing x. For 0.4≤x≤0.7, ferromagnetic (FM) phase is observed below 140 K and both the ordering temperature Tc and Curie-Weiss temperature θp decrease with increasing x, showing the weakening of in-plane FM magnetic coupling between Mn moments due to the substitution of Mn by nonmagnetic Cu. For 0.8≤x≤1, samples exhibit only paramagnetic behavior. The types of magnetic order in this series are basically consistent with the criterion that FM (AFM) phase is favored when intralayer Mn-Mn spacing R Mn-Mn a is greater (smaller) than a critical value of 2.865 Å. A magnetic phase diagram is constructed for this compound series.