Chemical pressure manipulation of ferromagnetism in magnetic semiconductor Ba(Zn,Mn,Cu)₂As₂

We report the manipulation of ferromagnetism in magnetic semiconductor Ba(Zn,Mn,Cu)₂As₂ through chemical pressure. The substitutions of Sr for Ba and Sb for As introduce positive and negative chemical pressures, respectively; neither Sr doping nor Sb doping change the tetragonal crystal structure. Based on Ba(Zn_0.75Mn_0.125Cu_0.125)₂As₂ with T_C ∼ 34 K, 10% Sr/Ba substitutions significantly improve T_C by ∼ 15% to 39 K, whereas 10% Sb/As substitutions substantially reduce T_C by ∼ 47% to 18 K. The AC magnetic susceptibility measurements indicate that Sr-doped and Sb-doped samples evolve into a spin glass state below the spin freezing temperature T_f. Electrical transport measurements demonstrate that Sr-doped specimens retain semiconducting behavior; additionally, they display a significant negative magnetoresistance effect under applied magnetic fields and the magnetoresistance reaches ∼ −19% at 8 T.