Complementarity of perturbations driving insulator-to-metal transition in a charge-ordered manganite

Abstract

Modulation of charge carrier dynamics and hence electrical conductivity of solids by photoexcitation has been a rich field of research with numerous applications. Similarly, electric and magnetic field assisted enhancement of conductivity are of fundamental importance and technological use.

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“…Clearly, the heating curve of the phototransformed state is similar to the heating curve for samples with y < 0.45 (see figure 1) all of which exhibit an MI transition at T MI C , the value of which decreases with increasing y. A similar effect induced by pulsed laser irradiation has already been demonstrated [34]. The above observation can be explained only in terms of a photo-induced collapse of the COI state into a metallic state, which is presumably FM.…”

“…Although the explicit signature of charge ordering is absent in our R-T measurements, electron diffraction experiments on the y = 0.275 sample clearly show the onset of charge ordering at 210 K [29]. The intrinsic IMT is also a sensitive function of applied magnetic and electric fields, and a complementarity of these externally applied perturbations has been reported for films with y = 0.45 [34]. For the y = 0.45 sample, electric fields of strength ≈0.6 and 10 kV cm −1 induce IMT at 30 and 80 K respectively, while the maximum bias field strength for the samples in figure 1 was less than 0.07 kV cm −1 .…”

“…In the inset of figure 4 we plot T as a function of light intensity I which yields d T /dI ≈ 1.7 K W −1 cm 2 . It should be pointed out that we have observed the photo-induced transitions at intensities as low as 24 mW cm −2 in La 0.175 Pr 0.45 Ca 0.375 MnO 3 thin films [34] for which the expected temperature rise is only ≈0.1 K. In figure 5(a) we show the temperature dependence of resistance of a 2000Å epitaxial film of LaMnO 3 (LMO) measured in the dark and upon photo-illumination (I = 800 mW cm −2 , hν = 2.8 eV). LMO films are insulating with no ordering of charge but nearly the same resistance as that of the LPCMO thin films described earlier (figure 2).…”

“…LPCMO single crystals also exhibit a decrease in the resistance for bias fields ∼0.2 kV cm −1 below 50 K [35]. The magnetization measurements done in an applied inplane field of 1000 G on a sample of identical composition and thickness reveal an FM state below ∼150 K [34]. Although in these measurements the magnetic signal from the La 0.175 Pr 0.45 Ca 0.375 MnO 3 film is masked heavily by the signal from the NGO substrate, nevertheless the magnetic moment per Mn ion falls far short of the fully aligned value of 3.625 μ B .…”

Large photoconductivity and light-induced recovery of the insulator-metal transition in ultrathinLa0.7Ce0.3MnO3−δBeyreuther1, Thiessen2, Grafström3 et al. 2009Phys. Rev. B214340View full textAdd to dashboardCite

“…The original state can be recovered only by heating. PPC phenomena have been observed in metallic ͑mostly oxygen deficient͒ [7][8][9][10][11] and in insulating charge-ordered 12,13 ͑CO͒ manganites. Since the effect is often observed in oxygen-deficient samples, it was suggested that the underlying mechanism might be similar as in oxygen-deficient YBa 2 Cu 3 O 7−␦ thin films ͑Ref.…”