Orthorhombic distortion and novel magnetic phase separation in Pr0.5Eu0.5MnO3

Abstract

Spin dynamics of (Pr0.5-xCex)Ca0.5MnO3 (x=0.05, 0.10, and 0.20) system studied by muon spin relaxation J. Appl. Phys. 112, 073911 (2012); 10.1063/1.4754848Magnetic field-induced metamagnetic transitions of Pr0.5Ca0.5Mn0.97Ga0.03O3Structural and magnetic measurements were done on polycrystalline manganite, Pr 0:5 Eu 0:5 MnO 3 . The Rietveld refinement of the x-ray powder diffraction pattern at room temperature suggests considerable Jahn-Teller distortion due to ionic size mismatch of the isovalent ions. Dc and ac magnetometry suggest a disordered antiferromagnetic (AFM) state, exhibiting glassy magnetic behavior at low temperature. Cooling in a static magnetic field reveals a considerable shift of the magnetic hysteresis loops, a typical manifestation of exchange bias. Interestingly, we observe the absence of training effect in exchange bias. The temperature, cooling field dependent study of exchange bias, and absence of exchange bias in La 0:5 Eu 0:5 MnO 3 suggest a novel low temperature phase separation between a disordered AFM phase induced by the Mn moments and another highly anisotropic phase involving ordering related to the rare-earth moments. It appears that this unique magnetic ground state exhibiting exchange bias is a consequence of the structural distortion inherent in the system.

A Griffiths-like phase in antiferromagnetic R0.5Eu0.5MnO3(R = Pr, Nd, Sm)

“…A satisfactory fit is obvious from the difference plot which also demonstrates the absence of secondary phase in the compound. Similar satisfactory fits (not shown) are also obtained for the other two samples in accordance with our previous reports [16,17]. The lattice parameters (a, b and c) and unit cell volumes (V), shown in table 1, agree well with the reported values of similar isovalent doped RE manganites [18,19,21].…”

“…The ZFC-curve (measured in a warming cycle with a field after cooling in zero field) presents a sharp peak at ∼62 K, while a rising feature is observable with decreasing T in the FC-curve (measured in a warming cycle with a field after cooling in the same field) showing a strong irreversibility between ZFC and FC curves. Similar behaviour is evident in the other two compositions [16,17]. The sharp peak is indicative of an A-type AFM-like transition (T N ) which has also been observed in similar isovalent doped RE manganites such as Eu 1−x Y x MnO 3 [30], La 1−x Eu x MnO 3 [20] and La 1−x Gd x MnO 3 [24].…”

“…χ dc (T) measured in a high dc magnetic field (H) ∼30 kOe is fitted with the modified Curie-Weiss (CW) law, χ dc (T) = χ 0 + C/(T − CW ), where χ 0 is a constant, C is the Curie constant and CW is the CW temperature. The second term on the right is the standard Curie-Weiss law while the first term accounts for the T-independent Van Vleck paramagnetism occurring because of Eu 3+ [12,16,17]. A least square fit provides considerable values of χ 0 for all the compounds.…”