Magnetoelectric Coupling in Ni–Mn–In/PLZT Artificial Multiferroic Heterostructure and Its Application in Mid-IR Photothermal Modulation by External Magnetic Field

Here we show fabrication of an artificial multiferroic heterostructure by a sputter deposited ferromagnetic Ni0.5Mn0.35In0.15 (Ni–Mn–In) layer followed by a ferroelectric Pb0.96La0.04(Zr0.52Ti0.48) O3 (PLZT) layer on silicon substrate. Room temperature X-ray diffraction of the heterostructures revealed a polycrystalline austenitic L21 phase formed at the bottom Ni–Mn–In layer and tetragonal phase formed on the top PLZT film. The Raman spectra of the sample exhibits the presence of Raman active modes at ∼322 and ∼622 cm–1, which emerge from the top PLZT layer, and with an additional hump in the range from ∼1227 to 1314 cm–1 due to either La vacancies in PLZT or formation of bonds at NiMnIn and PLZT interface. The ferroelectric behavior of the fabricated heterostructure is demonstrated using piezoresponse force microscopy (PFM) analysis and conventional P–E loop measurement. Room temperature magnetic force microscopy (MFM) and magnetic hysteresis measurements confirm the existence of ferromagnetism in the bilayer with a coercive magnetic field of 2EC 12–240.2 Oe and saturated magnetization of ∼121.55 emu/cc. Additionally this film also shows strong magnetoelectric coupling and exhibits an appreciable coupling coefficient (α) of 1.36 V/(cm Oe) measured by dynamic magnetic measurement. Further, the Ni–Mn–In/PLZT heterostructure exhibits excellent mid-infrared (1200–1400 cm–1, ∼7.1–8.3 μm) response with a maximum sensitivity of 1.65% at 1300 cm–1. The mid-infrared response is fastest for 1300 cm–1 infrared pulses with average response times of 3.4 s (rise) and 2.1 s (fall). Furthermore, it is also observed that the response time can be reduced by more than one and a half times (rise time, 1.5 s; fall time, 1.2 s) under the presence of 100 mT static magnetic field. Hence this phenomenon offers extra degrees of freedom to control the detection speed of a detector. We hypothesize this occurs in this case due to the rapid migration of charge carriers with minimal chance of recombination or loss due to spin polarization of charge carriers and increase in internal electric field of the ferroelectric layer under magnetic field due to strong magnetoelectric coupling in the Ni–Mn–In/PLZT multiferroic heterostructure. These results demonstrate that the Ni–Mn–In/PLZT multiferroic heterostructures have great potential to be used as mid-infrared detectors whose detection speed can be altered by magnetic field.