Critical behavior of La0.87K0.13MnO3 manganite

Gamzatov, A. G.; Aliev, A. M.; Khizriev, K. Sh.; Kamilov, I. K.; Mankevich, A. S.

doi:10.1016/j.jallcom.2011.05.065

Cited by 10 publications

(2 citation statements)

References 26 publications

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“…If the spread in critical temperatures is comparable to the size of the critical region, it becomes difficult to assign definite critical exponents to the system. This is also true if one tries to determine the universality class from the critical behavior of the specific heat, which has been suggested as a better alternative [27]. Here we will show that direct measurements of the isothermal entropy change not only allows for a reliable determination of the critical temperature but also gives insight into the spin-lattice coupling of the system.…”

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confidence: 63%

Nonuniversal scaling of the magnetocaloric effect as an insight into spin-lattice interactions in manganites

et al. 2016

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We measure the magnetocaloric effect of the manganite series La 0.67 Ca 0.33−x Sr x MnO 3 by determining the isothermal entropy change upon magnetization, using variable-field calorimetry. The results demonstrate that the field dependence of the magnetocaloric effect close to the critical temperature is not given uniquely by the critical exponents of the ferromagnetic-paramagnetic phase transition, i.e., the scaling is nonuniversal. A theoretical description based on the Bean-Rodbell model and taking into account compositional inhomogeneities is shown to be able to account for the observed field dependence. In this way the determination of the nonuniversal field dependence of the magnetocaloric effect close to a phase transition can be used as a method to gain insight into the strength of the spin-lattice interactions of magnetic materials. The approach is shown also to be applicable to first-order transitions.

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confidence: 63%

Nonuniversal scaling of the magnetocaloric effect as an insight into spin-lattice interactions in manganites

et al. 2016

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“…When T * ≤ 0.5 K, with the increase of T * , σ 2 drops drastically to the minimum, while G enhances quickly; when T * > 0.5 K, as T * increases, σ 2 is almost unchanged and the enhancement of G is comparatively slow, indicating that the data no longer diverge much from the Gaussian prediction. Thus the width of the critical region of ZnV 2 O 4 is T * = 0.5 K. In the critical region, the critical behavior is further analyzed by renormalization-group theory, the excess specific heat could be described as [26][27][28] ∆C P = A ± |t| −α (1 + F ± |t| 0.5 ), (7) where t = (T − T M )/T M is the reduced temperature, A + and A − are the critical amplitudes of specific heat above and below the transition temperature, respectively, α is the critical exponent, and F + and F − are the amplitudes of the antiferromagnetic empirical correction term. The critical exponent α depends on dimension d and order parameter n of the system.…”

Section: Antiferromagnetic Transition Regionmentioning

confidence: 99%

Phase transition and critical behavior of spin–orbital coupled spinel ZnV ₂ O ₄

Wang

Zhu

et al. 2016

Chinese Phys. B

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We present the temperature-dependent susceptibility and specific heat measurement of spinel ZnV 2 O 4 . The structural transition with orbital ordering and the antiferromagnetic transition with spin ordering were observed at 50 K and 37 K, respectively. By analysis of the hysteresis behavior between the specific heat curves obtained in warming and cooling processes, the structural transition was confirmed to be the first-order transition, while the antiferromagnetic transition was found to be of the second-order type. At the structural transition, the latent heat and entropy change were calculated from the excess specific heat, and the derivative of pressure with respect to temperature was obtained using the Clausius-Clapayron equation. At the magnetic transition, the width of the critical fluctuation region was obtained to be about 0.5 K by comparing with Gaussian fluctuations. In the critical region, the critical behavior was analyzed by using renormalization-group theory. The critical amplitude ratio A + /A − = 1.46, which deviates from the 3D Heisenburg model; while the critical exponent α is −0.011, which is close to the 3D XY model. We proposed that these abnormal critical behaviors can be attributed to strong spin-orbital coupling accompanied with the antiferromagnetic transition. Moreover, in the low temperature range (2-5 K), the Fermi energy, the density of states near the Fermi surface, and the low limit of Debye temperature were estimated to be 2.42 eV, 2.48 eV −1 , and 240 K, respectively.

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Specific heat and magnetocaloric effect of Pr1−x Ag x MnO3 manganites

et al. 2013

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The magnetocaloric effect in alternating magnetic fields has been investigated in Pr 1-x Ag x MnO 3 manganites with x=0. 05-0.25. The stepwise reversal of the sign of the magnetocaloric effect has been revealed in a weakly doped sample (x=0.05) at low temperatures (~80 K). This reversal is attributed to the coexistence of the ferromagnetic and canted antiferromagnetic phases with different critical temperatures.The physical properties of Pr 1-x Ag x MnO 3 praseodymium manganites (A is a univalent metal Na, K, Ag, etc.) are strongly different from the properties of manganites of other rare_earth metals (La, etc.). This system does not undergo a metalinsulator phase transition characteristic of other manganites and its existence region is much narrower, x≤0.25 [1][2][3]. Moreover, the Curie temperature T C of this system is lower than 136 K [2] owing to a large difference between the ion radii of Pr and substituting cations Na, K, and Ag (r Pr =0.099 nm, r Na =0.116 nm, r K =0.138 nm, and r Ag =0.115 nm), which causes local distortions of the crystal lattice; a decrease in the Mn-O-Mn valence angle; a weakening of the exchange interaction; and, as a result, a decrease in T C [4].The effect of the substitution of univalent alkali metal atoms Na and K for Pr atoms on the electric and magnetic properties was analyzed in [1,2]. The structure and magnetic and electric properties of Pr 1-x Ag x MnO 3 were investigated in [3]. According to [3], the behavior of the electric resistivity ρ(T) down to low temperatures is of a semiconducting character and the temperature dependence of the magnetic susceptibility has anomalies characteristic of the paramagnetferromagnet phase transition. For this reason, Pr 1-x Ag x MnO 3 was classified as a ferromagnetic insulator whose Curie temperature depends on the doping level.In this work, we report the experimental results for the specific heat C P and magnetocaloric effect ΔT of the Pr 1-x Ag x MnO 3 ceramic samples with x=0.05, 0.1, 0.15, and 0.25 for temperatures T=77-300 K. The technology of the manufacture of the samples and their magnetic and electric properties were described in [3]. According to the measurements of the magnetic susceptibility, the paramagnetferromagnet phase transition is observed in all of the samples and T C depends nonmonotonically on the doping level: it increases sharply at weak doping, reaches a maximum at x=0. 15-0.20, and decreases smoothly with a further increase in the doping level.The specific heat was measured by the ac calorimetry method [5] and, to directly measure the magnetocaloric effect, a special method based on the measurement of the amplitude of sample temperature oscillations in the presence of a weak ac magnetic field was developed [6].The essence of this method is as follows. The external alternating magnetic field H=H 0 cosωt (H 0 is the amplitude and ω is the cyclic frequency) applied to a magnetic material induces oscillations of its temperature T=T 0 cos(ωt+ϕ), where ϕ is the phase shift of oscillations of the temperature wit...

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Critical behavior of La0.87K0.13MnO3 manganite

Cited by 10 publications

References 26 publications

Nonuniversal scaling of the magnetocaloric effect as an insight into spin-lattice interactions in manganites

Nonuniversal scaling of the magnetocaloric effect as an insight into spin-lattice interactions in manganites

Phase transition and critical behavior of spin–orbital coupled spinel ZnV ₂ O ₄

Specific heat and magnetocaloric effect of Pr1−x Ag x MnO3 manganites

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Critical behavior of La0.87K0.13MnO3 manganite

Cited by 10 publications

References 26 publications

Nonuniversal scaling of the magnetocaloric effect as an insight into spin-lattice interactions in manganites

Nonuniversal scaling of the magnetocaloric effect as an insight into spin-lattice interactions in manganites

Phase transition and critical behavior of spin–orbital coupled spinel ZnV 2 O 4

Specific heat and magnetocaloric effect of Pr1−x Ag x MnO3 manganites

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Phase transition and critical behavior of spin–orbital coupled spinel ZnV ₂ O ₄