Ferromagnetism and high magnetic moments induced by Ba substitution for Ca in charge ordered Nd0.5Ca0.5MnO3

The magnetic properties of the Nd_0.5Ca_0.5−xBa_xMnO₃ series have been investigated. Similar to the Pr_0.5Ca_0.5−xBa_xMnO₃ series (Raveau et al., J. Phys.: Condens. Matter 15 (2003) 7055), the substitution of Ba for Ca can also induce a ferromagnetic (FM) ground state and sharp magnetization steps at low temperature (2.5 K) in the Nd ones. The FM fraction first quickly increases with x due to the local ‘counter-distortion’ effect introduced by barium cations, reaches a maximum value of 26% for x = 0.03, and then slowly decreases as more Ba is introduced where the A-site size mismatch has increased dramatically. In comparison with the Pr series, the Nd series exhibit a greater ability to induce ferromagnetism. When the magnetic field is increased, for low substitution levels (x < 0.06) the latter series show higher magnetizations and lower critical fields where the magnetization steps appear. A possible interpretation for this behavior is that the Nd-Mn magnetic interactions can destabilize the antiferromagnetic structure and favour the development of FM domains.