Electronic and magnetic properties of R0.5A0.5MnO3 compounds (R = Gd, Dy, Ho, Er; A = Sr, Ca)

Electronic and magnetic properties of the perovskitelike compounds of R(0.5)A(0.5)MnO(3) (R = Gd, Dy, Ho, Er; A = Sr, Ca) have been studied by measuring lattice parameter, electrical resistivity, magnetic susceptibility, and magnetization. All the Sr-doped compounds show a transition from a paramagnetic insulator to a spin-glasslike insulator at T-g, even though the manganite La0.5Ca0.5MnO3, with nearly the same tolerance factor t, have been shown by others, to have different transitions. On the other hand, all the Ca-doped compounds show a charge-ordering transition at T-CO and show a transition from a paramagnetic insulator to a canted antiferromagnetic insulator and/or a spin-glass-like insulator at T-CA below T-CO. These transition temperatures decrease with decreasing t. in the compound of Gd0.5Ca0.5MnO3, the collapse of the charge ordering has been observed under a pulsed high magnetic field of 45 T at 4.2 K. On the other hand, in the compound of Gd0.5Sr0.5MnO3, the magnetization process depends on the strength of magnetic field. These electronic and magnetic properties depend not only on the tolerance factor but also the Variance (second moment) of the A-site ion radii distribution.