Observation of Griffiths phase, critical exponent analysis, and magnetic behavior in Bi-doped <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">La</mml:mi><mml:mrow><mml:mn>0.67</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi mathvariant="normal">Ca</mml:mi><mml:mrow><mml:mn>0.33</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi mathvariant="normal">MnO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>
Arpit Gaur, Ankita Tiwari, Gurmeet Singh, Rabindra Nath Mahato
Abstract
The nanocrystalline ${\mathrm{La}}_{0.67\ensuremath{-}x}{\mathrm{Bi}}_{x}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}$ ($x$ = 0.0, 0.1) samples were synthesized using a citrate complex method. The synthesized samples crystallizes in single phase and orthorhombic crystal structure with Pbnm space group. The nanocrystalline ${\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}$ (LCMO) exhibits significant second-order paramagnetic (PM) to ferromagnetic (FM) phase transition, whereas weak second-order phase transition (SOPT) was observed for ${\mathrm{La}}_{0.57}{\mathrm{Bi}}_{0.1}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}$ (LBCMO). Magnetic entropy and Landau analysis have been used for the confirmation of order of transition in the vicinity of transition temperature (${T}_{c}$). The Griffiths phase (GP), which was determined by the temperature-dependent inverse susceptibility (${\ensuremath{\chi}}^{\ensuremath{-}1}$) data, demonstrated a strong influence on La-site chemical substitution. Dimeron model is used to explain GP behavior for the samples. Temperature-dependent resistivity [$\ensuremath{\rho}$($T$)] also suggests the existence of dimeron formation above metal-insulator transition temperature ($T>{T}_{MI}$). A an unusual magnetic state also have been observed within the nonlinear region of Arrott plots for $T>{T}_{c}$. Using information on the intrinsic magnetic field, the critical behavior of the LBCMO sample was examined close to its Curie temperature. The critical exponents $\ensuremath{\beta}, \ensuremath{\gamma}$, and $\ensuremath{\delta}$ are 0.3108, 1.02, and 4.2, respectively. The observed critical behavior is not following any universality class.