Influence of charge and magnetic ordering on the insulator-metal transition in Pr1-xCaxMnO3

Charge-ordering breakdown dynamics and ferromagnetic resonance studies ofB-site Cu diluted Pr1‒xSrxMnO3

Here, we report the influence of Jahn-Teller active Cu substitution on the charge-ordering (CO) characteristics of one of the well-known manganite Pr0.45Sr0.55MnO3(S55) with a distorted tetragonal structure. Magnetization studies unveil a complex magnetic phase diagram for S55, showing distinct temperature ranges corresponding to various magnetic phases: a ferromagnetic phase dominated by the Double Exchange interaction withTC∼ 220.5 K, an antiferromagnetic phase belowTN∼ 207.6 K induced by CO with a transition temperature ofTCO∼ 210 K consistent with the specific heatCP(T) data, and a mixed phase in the rangeTNTN(T Collapse

Key Words

• Jahn-Teller effect
• antiferromagnetism
• charge-ordering
• ferromagnetic resonance
• manganites
• perovskites

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Affiliation(s)

A Bordoloi Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
S K Jena Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
P Tiwari Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
A Datta Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
B Weise Leibniz-IFW Dresden, Institute for Complex Materials, D-01069 Dresden, Germany
R Medwal Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh, India
R S Rawat Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, Singapore 637616, Singapore
S Thota Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India

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Structural, magnetic, electrical and dielectric properties of Pr0.8Na0.2MnO3 manganite

The orthorhombic Pr_0.8Na_0.2MnO₃ ceramic was prepared in polycrystalline form by a Pechini sol–gel method and its structural, magnetic, electrical and dielectric properties were investigated experimentally. A structural study confirms that the sample is single phase. Magnetic measurements show that the sample is a charge ordered manganite. The sample undergoes two successive magnetic phase transitions with the variation of temperature: a charge ordering transition occurred at T_CO = 212 K followed by a paramagnetic (PM) to ferromagnetic (FM) transition around T_C = 115 K. From an electrical point of view, a saturation region was marked in the conductivity as a function of temperature σ(T) curves at a specific temperature. The dc-conductivity (σ_dc) reaches a maximum value at 240 K. The obtained results are in good agreement with the temperature dependence of the average normalized change (ANC). We found that the conduction mechanism was governed by small polaron hopping (SPH) in the high temperature region and by variable range hopping (VRH) in the low temperature region. Complex impedance analysis indicates the presence of a non-Debye relaxation phenomenon in the system. Also, the compound was modeled by an electrical equivalent circuit. Then, the contribution of the grain boundary in the transport properties was confirmed.

The orthorhombic Pr_0.8Na_0.2MnO₃ ceramic was prepared in polycrystalline form by a Pechini sol–gel method and its structural, magnetic, electrical and dielectric properties were investigated experimentally.

Metal-Organic Chemical Vapor Deposition (MOCVD) Synthesis of Heteroepitaxial Pr0.7Ca0.3MnO3 Films: Effects of Processing Conditions on Structural/Morphological and Functional Properties

Calcium-doped praseodymium manganite films (Pr_0.7Ca_0.3MnO₃, PCMO) were prepared by metal-organic chemical vapor deposition (MOCVD) on SrTiO₃ (001) and SrTiO₃ (110) single-crystal substrates. Structural characterization through X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) analyses confirmed the formation of epitaxial PCMO phase films. Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) characterization was used to confirm lateral and vertical composition and the purity of the deposited films. Magnetic measurements, obtained in zero-field-cooling (ZFC) and field-cooling (FC) modes, provided evidence of the presence of a ferromagnetic (FM) transition temperature, which was correlated to the transport properties of the film. The functional properties of the deposited films, combined with the structural and chemical characterization collected data, indicate that the MOCVD approach represents a suitable route for the growth of pure, good quality PCMO for the fabrication of novel spintronic devices.

Microscopic theory of longitudinal sound velocity in charge ordered manganites

A microscopic theory of longitudinal sound velocity in a manganite system is reported here. The manganite system is described by a model Hamiltonian consisting of charge density wave (CDW) interaction in the e(g) band, an exchange interaction between spins of the itinerant e(g) band electrons and the core t(2g) electrons, and the Heisenberg interaction of the core level spins. The magnetization and the CDW order parameters are considered within mean-field approximations. The phonon Green's function was calculated by Zubarev's technique and hence the longitudinal velocity of sound was finally calculated for the manganite system. The results show that the elastic spring involved in the velocity of sound exhibits strong stiffening in the CDW phase with a decrease in temperature as observed in experiments.