Improved Scaling of the Magnetic Heat Capacity in La0.85Ag0.15MnO3 Manganite

Abstract

The heat capacity in a La0.85Ag0.15MnO3 manganite was measured near Curie temperature TC under the applied magnetic fields up to 26 kOe to study scaling critical behavior and obtain universality class. The conventional scaling fails in application to the manganites with a hysteresis and the strong sensitivity of TC to a magnetic field. But the application of the improved scaling procedure designed by us allows of yielding the good scaling the magnetic heat capacity in La0.85Ag0.15MnO3, which may belong to a new universality class for systems with the strong spin-orbital coupling of t2g-electrons–Double 3D-Heisenberg with the critical exponent of the heat capacity α = −0.23 and the critical exponent of the correlation radius ν = 0.7433. This new universality class is consistent with the crystal, magnetic and orbital symmetries for the La0.85Ag0.15MnO3. Scaling failure in the vicinity of TC in the range of t/H1/2ν ≈ [−0.033; 0.024] is understood by finite-size and other disordering effects when T → TC. It is remarkable that finite-size effect is consistent with grain size, L ≈ 50 μm, in the La0.85Ag0.15MnO3. The correlation radius, Ltν ≈ 30.28 A, estimated from the finite-size effect is of the same order of magnitude with the sizes of the ferromagnetic fluctuations and drops in manganites.