The present paper reports detailed structural and magnetic characterization of the low-bandwidth manganite Pr(1-x)Ca(x)MnO(3) (with x = 0.0-0.5) (PCMO) polycrystalline samples. With increasing Ca content, reduction of the unit cell volume and improvement in perovskite structure symmetry was observed at room temperature. Magnetic characterization shows the signature of coexisting AFM-FM ordering and spin-glass phase at the low doping range (x = 0.0-0.2) while increased hole doping (x = 0.3-0.5) leads to charge ordering, training effect and an irreversible metamagnetic phenomenon. The large irreversible metamagnetism in the CO phase of PCMO and the corresponding spin memory effect is a direct consequence of hysteretic first-order phase transition arising from the weakening of the CO state under the external magnetic field and trapping of the spins due to a strong pinning potential in the material.

Persistent photo-induced magnetization (PPM) in low bandwidth manganite Pr1−xCaxMnO3 (PCMO) thin film is reported in the low hole doped regime (x = 0.1). X-ray diffraction, x-ray photoelectron spectroscopy, and magnetic measurements in dark and under illumination on the as-grown, vacuum, and oxygen annealed thin films of PCMO showed that the PPM effect is strongly dependent on the crystal symmetry, low angle grain boundaries, and the Mn valence states in the material. Compared with the as-grown and vacuum annealed film, the oxygen annealed film shows much less low-angle grain boundaries, higher crystal symmetry, and long range ferromagnetic (FM) ordering and in this sample PPM is not significant. These results clearly indicate that in this large band gap material PCMO, photo-induced FM interaction mainly arises due to improved domain-wall movement of the short range FM clusters. Significant PPM can be obtained for films with higher amount of grain boundaries, oxygen vacancies, and strain related defects.

5030 wileyonlinelibrary.com phase transition from antiferromagnetic (AFM) to ferromagnetic (FM) phase. [ 10 ] The CMR effect is huge for PCMO compounds where the CO phase is established, but the IMT transition demands a very high magnetic [ 9,11 ] or electric [ 8 ] fi eld which is not suitable for technological applications. Recently we reported that metamagnetic transition can be achieved in a relatively low magnetic fi eld for structurally improved PCMO ( x = 0.4 and 0.5) thin fi lms compared to the bulk samples. [ 12 ] Photoinduced melting of CO phase was previously demonstrated by Miyano et al. [ 13 ] and Takubo et al. [ 14,15 ] where an IMT was obtained under a strong electric fi eld. Recent report of Beaud et al. showed an ultrafast photoinduced breaking of CO phase at 100 °C temperature in PCMO x = 0.5 thin fi lm. [ 16 ] We have earlier observed an increase in FM phase at the cost of AFM phase under illumination at the low temperature coexisting FM-AFM phase of low-hole doped PCMO ( x = 0.1) thin fi lms [ 17 ] which could be related to IMT transition in this strongly correlated system. In this paper, we report that by illumination CMR of almost nine orders of magnitude can be achieved in PCMO ( x = 0.4) thin fi lm under 50% less applied magnetic fi eld compared to that in dark. We term this combined effect of light and magnetic fi eld on the sample resistance as magnetophotoresistance (MPR). Also by changing the measuring bias voltage, the required magnetic fi eld can be fi ne-tuned. The result could have signifi cant impact on the new generation of phase-change memories working under affordable conditions. ResultsThe PCMO thin fi lm samples for this study were selected to have considerably strong CO phase with metamagnetic AFM to FM transition. The two fi lms were chosen based on their sizable difference in magnetic fi eld required for AFM to FM transition, for a better insight of the illumination effects on different strengths of CO phases (see the Supporting Information). The sample with the weaker CO phase is PCMO x = 0.4 with in situ annealing treatment at 500 °C, called p40-500. The stronger CO phase is on the PCMO x = 0.5 sample with in situ annealing treatment at 700 °C, called p50-700. More detailed information of the samples is given in the Experimental Section.The magnetoresistive measurements were executed with a standard two-point connection in Quantum Design physical property measurement system (PPMS) with fi beroptic Photoinduced Colossal Magnetoresistance under Substantially Reduced Magnetic FieldTomi Elovaara , * Sayani Majumdar , Hannu Huhtinen , and Petriina Paturi The colossal magnetoresistive insulator to metal switching of almost nine orders of magnitude under the signifi cantly reduced magnetic fi eld is achieved by illumination for the low bandwidth manganite thin fi lms. Similarly, by changing the measuring bias voltage through the sample the required magnetic fi eld for insulator-metal transition can be further fi netuned. By applying a magnetic fi eld of suitable strength, the...

Epitaxial thin films of half-metallic oxide La0.7Sr0.3MnO3 (LSMO) have been grown in two crystalline orientations, one with the c-axis out-of-plane, the (001) orientation, and one with the c-axis in-plane, the (110) orientation. For the (110) oriented growth, there is no polar discontinuity at the substrate-film interface and hence no dead layer formation, which improves ferromagnetic interaction in the LSMO, making it highly attractive for spintronic applications. In our experiments, with x-ray diffraction, x-ray photoelectron spectroscopy and magnetic measurements, we have demonstrated that in the (110) oriented LSMO the lattice is more relaxed, leading to less deformation of electronic density around the La atom or in the MnO6 octahedra. This improved crystal and electronic structure improves the ferromagnetic properties of the films, making the Curie temperature higher by almost 15 K, which is of potential interest for spintronics. However, substrate strain induced magnetic anisotropy causes domain formation with out-of-plane components in these films, which poses some concern for practical spintronic devices.