Magnetic transformations in reentrant region of the x-T diagram of Li0.5Fe2.5-xGaxO4 spin-glass system

Reentrant spinels Li0.5Fe2.5-xGaxO4 with x=0.9 and 1.2 display peaks on the temperature dependences of heat capacity C at T-1 = 13.4 K (x = 0.9) and 14.2 K (x = 1.2) respectively, which are typical of a first-order phase transition. This transition is identified with the transformation of the collinear ferrimagnetic structure into a noncollinear structure preceding on the temperature scale the state of ferrimagnetic spin glass existing in the temperature range 0 K less than or equal to T less than or equal to T-f, where transition temperatures T-f are 9 K (x = 0.9) and 12 K (x = 1.2). (C) 1998 American Institute of Physics. [S1063-777X(98)01210-9]