Anomalous magnetic behavior in La2/3Ca1/3MnO3 near the critical point: stable clusters and crossover to uniform ferromagnetism

Studies on the Arrott plots of inhomogeneous first order magnetic phase transitions

“…The corresponding Arrott plots (H/M vs. M 2 ) around the transition temperature in these two cases are shown in figures 5 (b) and 5 (c). Similar results for the La(Fe,Mn,Si) 13 H system are shown in figure 6. Figure 6 (a) shows the M vs. T near the FM-PM phase transition ).…”

“…The material parameters used for the calculations are taken from references [42,43]. The parameters used are J = 1, η = 1.3, T 0 = 305 K and T C = 308 K for the La(Fe,Mn,Si) 13 H system [42] and J = 2, η = 1.25, T 0 = 265.9 K and T C = 268 K for the La 2/3 Ca 1/3 MnO 3 system [43]. Here the calculation details for the La 2/3 Ca 1/3 MnO 3 system are described.…”

“…The classical Landau theory of phase transitions is often used to study the magnetic phase transitions. According to the Landau theory the thermodynamic potential for magnetic phase transition is expressed as [11][12][13][14][15][16][17]…”

“…The behaviour of temperature dependence of the parameters a(T), b(T), c(T) determines (like when the parameters a and b changes their respective sign) first or second order nature of the underlying magnetic phase transition [12][13][14][15][16][17]. Generally, in the first approximations, a linear temperature variation of the parameters are considered, such as = a [11][12][13][14][15][16][17].…”

Magnetic properties of La1−xCaxCoO3 single crystals

“…Such step-like features observed also for x ¼ 0:15 were practically invisible for x ¼ 0:20: In Fig. 4 Amarel et al [28,29] observed also the effect of sequences of step-like features in the paramagnetic region of polycrystalline La 2/3 Ca 1/3 MnO 3 . It was suggested that low-field anomalies were due to the formation of spin clusters (consisting of several Mn 3+ ions sharing one or more extra holes).…”