Reinvestigation of Magnetic Structures for the Thermally Induced States of CuFe_<1-x>Al_xO_2 (x=0.00, 0.02 and 0.05) Using a Four-Circle Neutron Diffractometer(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

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We have reinvestigated the effect of non-magnetic impurity on thermally-induced magnetic orderings in geometrically frustrated triangular lattice antiferromagnets CuFe_<1-x>Al_xO_2 with x=0.00, 0.02 and 0.05, using a four-circle neutron diffractometer. Although we inferred in our previous work with a three-axis diffractometer that a proper screw type magnetic structure is realized in the intermediate-temperature (IM) phase of the samples with x=0.02 and x=0.05, in the present work we found that a sinusoidally amplitude-modulated magnetic structure with the magnetic moments canted by about 50° from the c axis toward the hexagonal <11^^-0> direction is realized. These experimental findings suggest that the quasi-Ising magnetic orderings in CuFeO_2 are stabilized not with the strong Ising anisotropy expected from the Ising-like successive magnetic phase transitions in CuFeO_2 but with the small Ising anisotropy added to strongly competing exchange interactions.
社団法人日本物理学会の論文
2005-05-15