Breakdown of the antiferrodistorsion Jahn-Teller ordering in K Dy(Mo O4)2 crystal in magnetic field: the intermediate phase formation

The layered crystal K Dy (Mo O4)2 has been investigated by means of polarization optics in the wavelength region 400-800 nm and in the external magnetic field applied along the direction of the maximum g-factor of the sites of one of the sublattices. A new field-induced structural phase transition was revealed at the temperature 7 K in the field H1 = 32 kOe. The mutual transformations between low- and high-temperature phases occur through a formation of the intermediate phase. It is supposed that intermediate phase has a modulated structure. The extrapolated temperature dependences of the transition fields H1 and H2 shown that the intermediate crystal phase has to exist at H = 0 un the temperature range from T1 = 11.5 K to T2 = 14.3 K as well