Neutron scattering studies on powder and single crystals have provided new evidences for unconventional magnetism in Cu2Te2O5Cl2. The compound is built from tetrahedral clusters of S = 1/2 <$E roman Cu sup 2+> spins located on a tetragonal lattice. Magnetic ordering, emerging at <$E T sub N~=~18,2> K, leads to a verv complex multi-domain, most likely degenerate, ground state, which is characterized by an incommensurate (ICM) wave vector k ~ [0,15, 0,42, 1/2]. The <$E roman Cu sup 2+> ions carry a magnetic moment of 0,67(1) <$E mu sub B "/" roman Cu sup 2+> at 1,5 К and form a four helices spin arrangement with two canted pairs within the tetrahedra. A domain redistribution is observed when a magnetic field is applied in the tetragonal plane (<$E H sub c~symbol Ы~0,5> T), but not for <$E H || c> up to 4 T. The excitation spectrum is characterized by two well-defined modes, one completely dispersionless at 6 meV, the other strongly dispersing to a gap of 2 meV. The reason for such complex ground state and spin excitations may be geometrical frustration of the <$E roman Cu sup 2+> spins within the tetrahedra, intra- and inter-tetrahedral couplings having similar strengths and strong Dzyaloshinski - Moriya anisotropy. Candidates for the dominant intra- and inter-tetrahedral interactions are proposed.

Індекс рубрикатора НБУВ: В368.313

Рубрики:

Магнітні властивості надпровідників

Шифр НБУВ: Ж14063 Пошук видання у каталогах НБУВ 

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