Thermal noise in linear damped systems

• Published in: IEEE transactions on magnetics Vol. 38; no. 5; pp. 3540 - 3544
• Main Author: Mallinson, J.C.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.09.2002; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Capacitors; Circuit noise; Damping; Dissipation; Electronics; Equivalent circuits; Exact sciences and technology; Fluctuation; Fluctuations; Frequency; Giant magnetoresistance; Linear systems; Low-frequency noise; Magnetic device characterization, design, and modeling; Magnetic devices; Magnetism; Magnetization; Noise; Noise shaping; Resistors; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Thermal noise; Magnetoresistive device; Fluctuations; spin dynamics and relaxation; Linear damping; magnetization fluctuation noise; Theoretical study; Magnetic head; Thermal noise; Giant magnetoresistance; Magnetic properties; Index Terms-Giant magnetoresistive (GMR) heads
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2002.802704

It is frequently assumed that estimating the noise, or thermal fluctuations, in a damped linear system necessarily depends on knowing the precise magnitude of the damping or energy dissipative component of the system. This paper proves that this notion is incorrect by considering the noise power of a resistor. It then shows that the magnetization fluctuation noise power of a spin-valve giant magnetoresistive head, a subject of considerable current interest, can be analyzed in a particularly simple and straightforward manner without knowing the exact value of the gyromagnetic damping factor.