Magnetic and nonmagnetic impurity effect on magnetic orderings of the isosceles-triangular-lattice antiferromagnet CuMnO_2

摘要

We have investigated the magnetic and the nonmagnetic impurity substitution effects on the magnetic ordering of a frustrated isosceles-triangular-lattice antiferromagnet CuMnO_2 by means of magnetic neutron diffraction measurements on Cu(Mn_(1-y)Ga_y)O_2. While the magnetic wave vector of the magnetic ground state of "magnetically"-substituted Cu(Mn_(1-x)Cu_x)O_2 with · = 0·04 is Q = (12 12 0), that in the "nonmagnetically"-substituted Cu(Mn_(1-y)Ga_y)O_2with · =0.05, 0.15 and 0.20 is Q = (1/2 1/2 1/2), which is identical to that of pure CuMnO_2. We discuss the influence of magnetic or nonmagnetic impurity substitution on the magnetic ordering of CuMnO_2, by comparing the results for Cu(Mn_(1-y)Ga_y)O_2with that for Cu(Mn_(1-x)Cu_x)O_2.