Critical behavior and magnetocaloric effect in ferromagnetic nano-crystalline Pr2CoMnO6

Abstract

To understand the nature of magnetic phase transition in nano-crystalline Pr2CoMnO6, in present study we have investigated the critical behavior and magnetocaloric effect. To estimate the critical exponents, various methods have been adopted like; the modified Arrott plots (MAP), the Kouvel-Fisher method (KF) and the critical isotherm analysis. This material shows a second order type a paramagnetic (PM) to ferromagnetic (FM) phase transition around 160 K. The critical exponents obtained from modified Arrott plots are β = 0.531, γ = 0.935 and Tc = 160 K. Kouvel-Fisher method gives the exponents as β = 0.533±0.001 with Tc = 160.72±0.03 K and γ = 0.932±0.003 with Tc = 160.15±0.05 K. The third exponent δ = 2.763±0.005 obtained from critical isothermal is in agreement with Wisdom scaling rule. The estimated critical exponents do not exactly match with any established universality class, however, the deduced exponent values suggest that spin interaction in the present material is close to mean-field model which suggests the existence of longrange ferromagnetic order in nano-crystalline Pr2CoMnO6. The reliability of critical exponents is checked by universal scaling hypothesis on magnetic data across Tc. We have calculated the magnetic entropy change from magnetic data and found maximum value of -∆S = 2.05 (J kg −1 K −1 ) for 50 kOe at 180 K. Moreover, field dependent change in magnetic entropy obeys scaling and also indicates that the magnetic interaction is close to mean-field type.

Observation of ferromagnetism in CeCr2Si2C single crystals

“…Δ S increases quickly and then decreases slowly upon increase in the temperature under different magnetic fields. This phenomenon is usually observed in a ferromagnet, further confirming the FM behavior of CeCr 2 Si 2 C. 24,35,36 The maximum value of the entropy change at 5 T is 0.084 J mol −1 K −1 , much lower than 2.75 J mol −1 K −1 at the same magnetic field for PrCr 2 Si 2 C, 24 ascribing to a different origin for FM order. In order to obtain the magnetic contribution ( C m ) associated with the FM phase transition, we extrapolated the nonmagnetic state heat capacity ( C nm ) down to 2 K as the sum of phonon contribution ( C ph ), and electron contribution ( C e ), C nm = C ph + C e .…”

“…DS increases quickly and then decreases slowly upon increase in the temperature under different magnetic elds. This phenomenon is usually observed in a ferromagnet, further conrming the FM behavior of CeCr 2 Si 2 C. 24,35,36 The maximum value of the entropy change at 5 T is 0.084 J mol −1 K −1 , much lower than 2.75 J mol −1 K −1 at the same magnetic eld for PrCr strong spin state. The small value of S mag is dominantly ascribed to the itinerancy of magnetic ions, which has been observed in iron pnictide superconductors.…”

Structural, magnetic, and magnetocaloric properties of R2NiMnO6 (R = Eu, Gd, Tb)

“… Compound Tc (K) ΔH (T) – ΔS M (J/kg K) RCP (J/kg) Ref. Eu 2 NiMnO 6 143 5 3.2 150 Present work Gd 2 NiMnO 6 130 5 3.7 182 Present work Tb 2 NiMnO 6 112 5 3.5 176 Present work Dy 2 NiMnO 6 101 5 3.4 175 20 Ho 2 NiMnO 6 93 5 3.7 194 20 Er 2 NiMnO 6 84 5 3.4 169 20 Pr 2 CoMnO 6 176 5 2.1 –- 36 Eu 2 CoMnO 6 123 6 3.3 –- 37 Dy 2 CoMnO 6 8.5 5 ...…”

Multifunctional behaviour in B-site disordered double perovskite EuPrCoMnO6

“…The value of δ is 3.0 for Mean Field Model, 4.8 for 3D Heisenberg Model, 4.82 for 3D Ising Model, and 5 for the Tricritical mean-field model [25]. Thus, the estimated value of the critical parameters for EPCMO follows the conventional mean-field scaling hypothesis [25,42,43]. The critical behavior study in other related DPs shows that the critical exponents are close to other conventional scaling hypotheses like 3D Ising model and 3D Heisenberg model [44,45].…”