Photoinduced Colossal Magnetoresistance under Substantially Reduced Magnetic Field

Abstract

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...

Optically Tunable Resistive-Switching Memory in Multiferroic Heterostructures

“…By controlling the strength of the EPS, i.e., the relative proportion of coexisting multiphases, in these complex oxides using various external stimuli, such as electric field, current, magnetic field, strain, light, etc., exotic functionalities are highly desired to develop energy-efficient multifunctional devices. As one of the most fascinating correlated oxides, perovskite manganites display large-scale EPS in the charge-ordering (CO) antiferromagnetic insulating phase, the ferromagnetic (FM) metallic phase, and/or the paramagnetic (PM) insulating phase [5][6][7][8][9][10]. Because of the strongly coupled nature of the lattice, charge, spin, and orbital degrees of freedom, the external stimuli can tip the subtle balance of free energy between the coexisting phases in manganites, leading to dramatic changes in physical properties.…”

Mechanical Modulation of Colossal Magnetoresistance in Flexible Epitaxial Perovskite Manganite

“…From previous studies, many factors including strain, oxygen vacancies, defects, and doping amounts would cause dramatically changes of its magnetic behaviors. [ 21,47,48,51,52 ] In Figure a, the magnetic hysteresis loops appear below 100 K implying the formation of ferromagnetic phase in our PCMO/F‐mica. A coercivity of 800 Oe can be detected at 10 K. As the temperature increases from 10 to 200 K, the hysteresis loops gradually change to linearity indicating a paramagnetic behavior.…”

“…The trend suggests an increasement of the melting field by reducing thickness of PCMO layer, and is accordant with the counterpart on rigid STO substrate. [20,21,[46][47][48] Mechanical flexibility is an essential factor which can modulate properties of nanostructure system dynamically. In our PCMO/F-mica system, with nanocolumn structure on the surficial area, different bending modes can highly congregate or separate columns and further strongly modulate transport properties.…”

“…The trend suggests an increasement of the melting field by reducing thickness of PCMO layer, and is accordant with the counterpart on rigid STO substrate. [ 20,21,46–48 ]…”

Evolution of photoinduced effects in phase-separated Sm0.5Sr0.5Mn1−yCryO3 thin films

“…In our previous work, the photoinduced effects in the CO La 0.5 Ca 0.5 MnO 3 film and the La 0.67 Ca 0.33 MnO 3 film with a typical metal-insulator phase transition, respectively, have been also revealed1920. Heretofore, the persistent and transient photoinduced effects observed in manganites mainly originate from the different mechanisms, such as the oxygen deficiency in mostly metallic states, the melting of CO state and the photoinduced demagnetization21222324. In particular, intrinsic mechanisms need to be uncovered further.…”