ACTA

Fast Bolometric Response of Bulk La_0.7Sr_0.3MnO₃ Electroceramic Structures

Yu.M. Nikolaenko^a, I.S. Maksimov^a, Yu.V. Medvedev^a, A.N. Ulyanov^a and A.M. Grishin^b
^a Donetsk Physico-Technical Institute of the National Academy of Sciences of the Ukraine, 72 R. Luxemburg, Donetsk, 340114, Ukraine
^b Dept. of Condensed Matter Physics, Royal Institute of Technology, 100 44, Stockholm, Sweden

Received: July 22, 1999; revised version December 10, 1999

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We report on the performance of a microwave electroceramic bolometer of hybrid La_0.7Sr_0.3MnO₃/Al₂O₃ (0.2×2×4 mm³) structure. The estimated thermal resistance of the bulk ceramic manganite film-single crystal sapphire interface is about 500 K/W at room temperature. This resistance is the main thermal barrier in the heat sink system and has been found to be slightly dependent on temperature. When compared with the high-T_c superconducting bolometers, the La_0.7Sr_0.3MnO₃ microwave electroceramic bolometer works in a more wide temperature range, from 77 K to 330 K, excluding the narrow temperature interval at the metal-insulator phase transition (T=230 K). The microwave electroceramic bolometer sensitivity and the time constant at room temperature have been found to be 0.1 V/W and 100 ms, respectively. To improve the bolometer performance the point contact has been fabricated by a break junction technique. The optimization of a microwave electroceramic bolometer design brought to a considerable improvement of basic bolometer characteristics. The microwave sensitivity was about 0.3 V/W and the time constant was less than 100 ns.

DOI: 10.12693/APhysPolA.97.991
PACS numbers: 07.57.Kp, 85.60.Gz, 72.15.Gd