Browsing by Author "Kiran, Dokala Ravi"

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    Magnetic and Electronic Structure of few Perovskites in the form of Bulk and 2D-Superlattices
    (2023) Kiran, Dokala Ravi
    Complex oxide systems with the perovskite structure are becoming highly significant for modern day magneto-electronic devices because of their unique magnetic and transport properties. Mainly, perovskites with 3d-4f transition metal-rare-earth perovskites have gained widespread attention due to the strong interplay between the lattice, electron spin, orbit, and crystal structure. The present work provides a glimpse of growth of such systems using pulsed laser deposition technique and their electronic/magnetic structure in the form of 2D superlattice structures. In particular, the current work deals with the superlattices of Pr0.7Ca0.3MnO3/SrTiO3]15 and [Pr0.5Ca0.5MnO3/SrTiO3]15 on (001) oriented SrTiO3 and LaAlO3 single crystal substrates. Elastic strain induced electronic reconstructions at the interface enhanced the interlayer ferromagnetic interactions in the case of x = 0.3 superlattices on SrTiO3 exhibiting the highest HK ∼ 9 kOe and K1 ∼ 8 × 105 erg/cc. Tunable spin–flopped transition (∼ 30 kOe), significant negative exchange-bias field (HEB ∼ 2.5 kOe), huge coercive field (HC ∼ 22 kOe) and large NM (ΔM ∼ 280 emu/mole) are the unique characteristic features of the Ce incorporated YCrO3 polycrystals. The H–T phase diagram, clearly distinguishes three prominent regions below the TN (∼ 150 K), viz (i) long-range canted AFM + weak FM phase ( ), (ii) Γ24 mixed phase and (iii) robust ) AFM + FM phases. Extensive magnetization measurements reveal the existence of orbital-ordering in Pr0.45-xYbxSr0.55MnO3 accompanied by antiferromagnetic (AFM) Néel temperature, at as low as 158 K below the high- (302 K) ferromagnetic (FM) phase. Irreversible metamagnetic transitions from the AFM-FM phase occurs for a specific composition Pr40 (x = 0.05) till T ≤ 220 K. The admixture of metastable states of AFM and FM is quite robust in the investigated system whereas AFM state is mediated by Yb3+ ions, while, the FM state arising by field driven thermo-magnetic kinetics. In the Gd0.9Ce0.1CrO3, overall magnetization M(T) undergoes a second transition at the low temperatures associated with spin-flip transition triggered by the critical field, HC = 200 Oe at (10 K). The system exhibits better magneto-entropy value -ΔSM = 42 J/Kg-K which is higher than the previously reported GdCrO3 values. The reduction in the Cr-O-Cr bond angle through the substitution of Ce3+ at the Gd3+ site deduce such betterment in the magnetic entropy value. The presented works find potential utility in the fields of magnetoelectronic, thermo-magnetic sensors and spintronic device applications.