NEW LINE OF THERMODYNAMIC PHASE-TRANSITIONS ON THE X-T DIAGRAM OF A DILUTE HEISENBERG-SYSTEM WITH SHORT-RANGE INTERACTIONS LI0.5FE2.5-XGAXO4

It is established on the basis of an investigation of the temperature dependences of the saturation magnetization sigma(S)(T) and the magnet ic contribution to the specific heat C-m(T) that in the reentrant regi on of the x-T diagram (0.9 less than or equal to x less than or equal to 1.5) of dilute iron spinels Li0.5Fe2.5-xGaxO4 there exists between the line of Curie points T-C(x) and the line of freezing temperatures T-f(x) another line of first-order phase transitions T-1(x) to a nonco llinear ferrimagnetic phase: T-C(x)less than or equal to T-1(x)less th an or equal to T-f(x). (C) 1998 American Institute of Physics. [S0021- 3640(98)00905-0].