Colossal magnetoresistive La-0.7(Pb1-xSrx)(0.3)MnO3 films for bolometer and magnetic sensor applications

We report on electrical and magnetic properties of a continuous series of s olid solutions La-0.7(Pb1-xSrx)(0.3)MnO3 prepared by the pulsed laser depos ition technique on LaAlO3 and SrTiO3 single crystals. Strict compositional control enables us to tailor the metal-to-semiconductor phase transition fr om 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 resonanc e linewidth ranges from 124 to 300 Oe, indicating low microwave loss and th e films uniformity. Noise spectroscopy performed in the 2 Hz-20 kHz range r eveals two components: Johnson noise (independent of frequency and bias cur rent) and excess 1/f noise proportional to the square of the bias current. Very low excess noise (normalized value gamma /n varying in the range from 10(-20) to 10(-22) cm(3)) has been achieved due to the epitaxial quality of the fabricated films. Using these films, an infrared radiation bolometer a nd weak magnetic field sensor have been built and tested. The bolometer res olves the noise equivalent temperature difference as low as 120 nK/root Hz at 30 Hz frame frequency, while the magnetic field sensor shows the noise e quivalent magnetic field difference of 50 mu Oe/root Hz at 1 kHz and optimu m bias magnetic field applied. (C) 2001 American Institute of Physics.