Jasnamol Pezhumkattil Palakkal

Multiple magnetic transitions, Griffiths-like phase, and magnetoresistance in La2CrMnO6

DC and AC magnetic measurements indicate the presence of multiple magnetic transitions arising from the competing magnetic interaction between Cr and Mn in the perovskite La2CrMnO6. Ferromagnetic and spin glass transitions are observed in La2CrMnO6. The material also has a Griffith-like phase with the occurrence of ferromagnetic short range correlations above TC. The system ultimately turns into paramagnetic at the Griffiths temperature 180 K. A combination of variable range hopping, and the nearest neighbor small polaron hopping governs the conduction mechanism in the material. A negative magnetoresistance of 22% at 105 K is observed for the material at 90 kOe which increases to 29% near 110 K and reduces gradually to zero on further increase in the temperature.

Observation of high-temperature magnetic transition and existence of ferromagnetic short-range correlations above transition in double perovskite La2FeMnO6

We present the observation of a high-temperature magnetic transition along with ferromagnetic short-range correlations (FSCs) in La2FeMnO6 perovskite system. XPS analysis confirmed the presence of Fe3+ and Mn3+ cations. Magnetization vs. temperature curves show two distinct transitions at TC1 ∼ 60 K and TC ∼ 425 K. Coercivity values of ∼1140 Oe and ∼35 Oe are observed at 2 K and 300 K respectively. Thermomagnetic analysis reveals the presence of FSCs in La2FeMnO6 up to T* = 570 K, well above the transition point, similar to a Griffiths-like phase (GP). The presence of ferromagnetic clusters in the paramagnetic region might be due to the intrinsic inhomogeneities associated with the structure, the quenched disorder related to the B-site cations and the antisite boundaries. The coefficient of lower temperature electronic specific heat is as high as 59.5 mJ mol−1 K−2. The electron spin resonance spectra show ferromagnetic resonance signals that point to the possibility of the presence of FSCs at room temperature. The material seems to be quite a promising candidate for some room temperature applications due to the possibility of the coexistence of functionalities like ferromagnetism, ferrimagnetism, GP, magnetotransport coupling, etc. in a single material.

Structural and magnetic properties of multiferroic Y2NiMnO6 double perovskite

ABSTRACT The double perovskite Y2NiMnO6 is prepared by a citrate-gel combustion method. The structural, magnetic and dc transport properties of Y2NiMnO6 are investigated systematically. A monoclinic crystal structure having space group P21/n is identified for the material from XRD. Magnetic structure is characterized by isothermal and thermomagnetic studies. The material possesses a ferromagnetic transition at 88 K. The dynamic magnetic structure of the material is analyzed using the ac susceptibility data. Resistivity data suggests the semiconducting behavior of the material. The work provides well advancement in researchers on potential material for spintronic applications.