AbstractWe report the synthesis and characterization of a bulk form diluted magnetic semiconductor Ba(Zn_1−2xMn_xCu_x)₂As₂"Equation missing" with the crystal structure identical to that of “122” family iron based superconductors and the antiferromagnet BaMn₂As₂. No ferromagnetic order occurs with (Zn, Mn) or (Zn, Cu) substitution in the parent compound BaZn₂As₂. Only when Zn is substituted by both Mn and Cu simultaneously, can the system undergo a ferromagnetic transition below T_C ~ 70 K, followed by a magnetic glassy transition at T_f ~ 35 K. AC susceptibility measurements for Ba(Zn_0.75Mn_0.125Cu_0.125)₂As₂ reveal that T_f strongly depends on the applied frequency with "Equation missing" and a DC magnetic field dependence of "Equation missing", demonstrating that a spin glass transition takes place at T_f. As large as −53% negative magnetoresistance has been observed in Ba(Zn_1−2xMn_xCu_x)₂As₂, enabling its possible application in memory devices.