Colossal magnetoresistive La0.7(Pb1−xSrx)0.3MnO3 films for bolometer and magnetic sensor applications

We report on electrical and magnetic properties of a continuous series of solid solutions La0.7(Pb1−xSrx)0.3MnO3 prepared by the pulsed laser deposition technique on LaAlO3 and SrTiO3 single crystals. Strict compositional control enables us to tailor the metal-to-semiconductor phase transition from 266 to 327 K, the maximum of temperature coefficient of resistance from 10.2% K−1 to 3.2% K−1, and maximum of magnetoresistance ratio at 7 kOe from 41% to 17% for x=0 and x=1 correspondingly. The ferromagnetic resonance linewidth ranges from 124 to 300 Oe, indicating low microwave loss and the films uniformity. Noise spectroscopy performed in the 2 Hz–20 kHz range reveals two components: Johnson noise (independent of frequency and bias current) and excess 1/f noise proportional to the square of the bias current. Very low excess noise (normalized value γ/n varying in the range from 10−20 to 10−22 cm3) has been achieved due to the epitaxial quality of the fabricated films. Using these films, an infrared radiation bolometer and weak magnetic field sensor have been built and tested. The bolometer resolves the noise equivalent temperature difference as low as 120 nK/√Hz at 30 Hz frame frequency, while the magnetic field sensor shows the noise equivalent magnetic field difference of 50 μOe/√Hz at 1 kHz and optimum bias magnetic field applied.