Magnetic phase diagram of ErCuSi studied by neutron diffraction and magnetic measurements

The magnetic phase diagram of the hexagonal ErCuSi (P6(3)/mmc) compound has been studied by neutron powder diffraction and magnetic measurement. Magne tic ordering occurs below T-N = 6.8 K and is associated with the wave vecto r, q = (1/12, 0, 0), with a temperature-independent length. The magnetic st ructure can be described by a transverse sine-wave-modulated arrangement of the Er moments oriented \\c with a maximum moment amplitude of 9.1(1) mu ( B)/Er atom or alternatively by an antiphase domain structure having three a mplitudes. At lower temperatures, T = 3.5 K, the appearance of the weak 3q harmonic indicates the onset of a squaring up transition to an antiphase do main structure with equal amplitudes. (C) 2001 Elsevier Science B.V. All ri ghts reserved.