Transport and magnetic properties of bulk and epitaxial thin film of Pr0.5Sr0.5MnO3
TL;DR: In this article, a thin film of Pr 0.5 Sr 0.3 was prepared by laser ablation technique and it showed a ferromagnetic ordering at 250 K for 200 G field followed by a second transition into an antiferromagnetic (AF) state around 150 K.
Abstract: A thin film of Pr 0.5 Sr 0.5 MnO 3 was prepared by laser ablation technique. The film (2500 A) shows a ferromagnetic (FM) ordering at 250 K for 200 G field followed by a second transition into an antiferromagnetic (AF) state around 150 K. By applying external fields, T C shifts to higher temperatures and the magnetisation maximum at T N shifts to slightly lower temperatures. The onset of the AF behavior in all fields up to 5 T is accompanied by a splitting of the cooling and the warming magnetisation data. The M ( T ) curve of the bulk sample shows a temperature hysteresis indicating a first order transition. The thermopower (TEP) of the bulk sample remains negative in the temperature range of 77–300 K. We studied the piezoresistance effect of the film under quasi hydrostatic pressure up to 4 kbar. The specific heat data of the bulk sample also indicates FM and AFM transitions by showing small peaks at the respective temperatures.
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TL;DR: In this paper, a complete critical behavior study of the paramagnetic to ferromagnetic transition in both manganites, which share many common features in their phase diagrams, has been independently obtained.
Abstract: Magnetic measurements have been performed on single crystalline samples of Pr 0.5 Sr 0.5 MnO 3 and Nd 0.5 Sr 0.5 MnO 3 to develop a complete critical behavior study of the paramagnetic to ferromagnetic transition in both manganites, which share many common features in their phase diagrams. The critical exponents β , γ and δ have been independently obtained. For Pr 0.5 Sr 0.5 MnO 3 these are β = 0.376, γ = 1.403 and δ = 4.72 which are in close agreement with the 3D-Heisenberg model ( β = 0.365, γ = 1.386 and δ = 4.80) while for Nd 0.5 Sr 0.5 MnO 3 they are β = 0.323, γ = 1.201, and δ = 4.77, which correspond to the 3D-Ising universality class ( β = 0.3265, γ = 1.237 and δ = 4.79). Magnetocrystalline anisotropies in Nd 0.5 Sr 0.5 MnO 3 are strong enough so that the magnetic transition is not compatible with the double exchange description while in Pr 0.5 Sr 0.5 MnO 3 they are not so relevant; in this last case the isotropic description is of application.
8 citations
TL;DR: In this article, the epitaxial (single crystal-like) Pr0.4La0.1Sr0.5MnO3 (PLSMO) and Nd0.35La 0.15Sr 0.5mnO 3 (NLSMO) thin films are prepared and characterized, and the electric and magnetic properties are examined.
Abstract: The epitaxial (single crystal-like) Pr0.4La0.1Sr0.5MnO3 (PLSMO) and Nd0.35La0.15Sr0.5MnO3 (NLSMO) thin films are prepared and characterized, and the electric and magnetic properties are examined. We find that both PLSMO and NLSMO have their own optimum deposition temperature (To) in their growing into epitaxial thin films. When the deposition temperature is higher than To, a c-axis oriented but polycrystalline thin film grows; when the deposition temperature is lower than To, the thin film tends to be a-axis oriented and also polycrystalline. The most important point is that for the epitaxial PLSMO and NLSMO thin films the electronic phase transitions are closely consistent with the magnetic phase transitions, i.e. an antiferromagnetic phase corresponds to an insulating state, a ferromagnetic phase corresponds to a metallic state and a paramagnetic phase corresponds to a semiconducting state, while for the polycrystalline thin films the electronic phase transitions are always not consistent with the magnetic transitions.
3 citations
TL;DR: In this paper, tetragonal and orthorhombic PSMO films were epitaxially grown on a [0, 0, 1]-oriented LaAlO3 substrate (LAO) and a BaTiO3 (BTO) substrate, respectively.
Abstract: Pr0.5Sr0.5MO3 (PSMO) films with tetragonal and orthorhombic structures were epitaxially grown on a [0 0 1]-oriented LaAlO3 substrate (LAO) and a BaTiO3 substrate (BTO), respectively. It was found that the M(T) curves of the tetragonal PSMO films exhibit one/two distinguished magnetic transition peaks depending on the thickness of the film, which is related to the competition between ferromagnetic (FM) and antiferromagnetic (AFM) interactions in the films. The tetragonal film shows an insulator-to-metal transition (MIT) as well as a metal-to-semiconductor transition with increasing temperature from 10 to 300 K, and the AFM insulating state of the film can be transformed into the metallic state under a magnetic field of 5 T due to the collapse of the AFM insulator state. For the orthorhombic film on BTO substrate, only a FM metallic state is observed without MIT from 10 to 300 K. In addition, a significant colossal magnetoresistance effect is observed with a wide temperature range from TC (182 K) to 10 K for the tetragonal films, while only around TC (240 K) for the orthorhombic films.
2 citations
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TL;DR: A negative isotropic magnetoresistance effect has been observed in thin oxide films of perovskite-like La0.67Ca0.33MnOx, which could be useful for various magnetic and electric device applications if the observed effects of material processing are optimized.
Abstract: A negative isotropic magnetoresistance effect more than three orders of magnitude larger than the typical giant magnetoresistance of some superlattice films has been observed in thin oxide films of perovskite-like La0.67Ca0.33MnOx. Epitaxial films that are grown on LaAIO3 substrates by laser ablation and suitably heat treated exhibit magnetoresistance values as high as 127,000 percent near 77 kelvin and ∼1300 percent near room temperature. Such a phenomenon could be useful for various magnetic and electric device applications if the observed effects of material processing are optimized. Possible mechanisms for the observed effect are discussed.
4,079 citations
TL;DR: The samples show a drop in the resistivity at the magnetic transition, and the existence of magnetic polarons seems to dominate the electric transport in this region.
Abstract: At room temperature a large magnetoresistance, \ensuremath{\Delta}R/R(H=0), of 60% has been observed in thin magnetic films of perovskitelike La-Ba-Mn-O. The films were grown epitaxially on ${\mathrm{SrTiO}}_{3}$ substrates by off-axis laser deposition. In the as-deposited state, the Curie temperature and the saturation magnetization were considerably lower compared to bulk samples, but were increased by a subsequent heat treatment. The samples show a drop in the resistivity at the magnetic transition, and the existence of magnetic polarons seems to dominate the electric transport in this region.
3,424 citations
TL;DR: A review of the literature on mixed-valence manganites, placing new results in the context of established knowledge of these materials, and other magnetic semiconductors, is given in this paper.
Abstract: Mixed-valence manganese oxides (R1-χAχ)MnO3 (R=rare-earth cation, A=alkali or alkaline earth cation), with a structure similar to that of perovskite CaTiO3, exhibit a rich variety of crystallographic, electronic and magnetic phases. Historically they led to the formulation of new physical concepts such as double exchange and the Jahn-Teller polaron. More recent work on thin films has revealed new phenomena, including colossal magnetoresistance near the Curie temperature, dense granular magnetoresistance and optically-induced magnetic phase transitions. This review gives an account of the literature on mixed-valence manganites, placing new results in the context of established knowledge of these materials, and other magnetic semiconductors. Issues addressed include the nature of the electronic ground states, the metal-insulator transition as a function of temperature, pressure and applied magnetic field, the electronic transport mechanisms, dielectric and magnetic polaron formation, magnetic localization, ...
1,757 citations
TL;DR: In this paper, the Curie temperature versus composition and saturation versus composition curves for mixed manganites with perovskite structures are given for LaMnO 3 CaMnNO 3, LaMmO 3 Ω(n 2 )n O(n 3 d )Mn 4+O(n 4 + O 3 2 2 ) and BaMn O 3 Ã 0, respectively.
Abstract: Various manganites of the general formula La 3+ Mn 3+ O 3 2− -Me 2+ Mn 4+ O 3 2− have been prepared in the form of polycrystalline products. Perovskite structures were found, i.a. for all mixed crystals LaMnO 3 CaMnO 3 , for LaMnO 3 SrMnO 3 containing up to 70% SrMnO 3 , and for LaMnO 3 BaMnO 3 containing less than 50% BaMnO 3 . The mixed crystals with perovskite structure are ferromagnetic. Curves for the Curie temperature versus composition and saturation versus composition are given for LaMnO 3 CaMnO 3 , LaMnO 3 SrMnO 3 , and LaMnO 3 BaMnO 3 . Both types of curves show maxima between 25 and 40% Me 2+ Mn 4+ O 3 2− ; here all 3 d electrons available contribute with their spins to the saturation magnetization. The ferromagnetic properties can be understood as the result of a strong positive Mn 3+ Mn 4+ exchange interaction combined with a weak Mn 3+ Mn 3+ interaction and a negative Mn 4+ Mn 4+ interaction. The Mn 3+ Mn 4+ interaction, presumably of the indirect exchange type, is thought to be the first clear example of positive exchange interaction in oxidic substances.
1,525 citations
TL;DR: In this paper, magnetoresistance data up to 20 T and magnetisation measurements on the mixed-valence cubic perovskite semiconductor Nd 05 Pb 05 MnO 3 were presented, which demonstrated that the material orders ferromagnetically below 184 K and that around and above this temperature the conductivity is dominated by hopping of localized magnetic polarons, with an activation energy ∼95 meV.
Abstract: We present magnetoresistance data up to 20 T and magnetisation measurements on the mixed-valence cubic perovskite semiconductor Nd 05 Pb 05 MnO 3 , which demonstrate that the material orders ferromagnetically below 184 K, and that around and above this temperature the conductivity is dominated by hopping of localized magnetic polarons, with an activation energy ∼95 meV
580 citations