Heinrich Georg Barkhausen (2 December 1881 – 20 February 1956) was a German physicist who established an influential research laboratory in Dresden. The phenomenon by which ferromagnetic domains align during magnetization and produce discrete acoustic changes due to rotations of the Weiss domains is named after his observations as the magnetic Barkhausen effect. He is also remembered in the Barkhausen criteria for electrical oscillators.
Life and work
Barkhausen was the son of district judge in Bremen. He studied at Bremen Gymnasium and showed interest in natural sciences from an early age. He worked as a railway engineering trainee before going to study at the Technical University of Munich (1901), Technische Universität Berlin (1902), the Ludwig-Maximilians-Universität München (1903) and the Humboldt University of Berlin, and obtained a doctorate at the University of Göttingen in 1907 with a thesis on the generation of oscillations.
He became the first professor of electrical engineering at the Technische Hochschule Dresden in 1911 When the magnetic field through a piece of ferromagnetic material like iron is changing, the magnetization of the material changes in a series of tiny discontinuous jumps, which can be heard as a series of clicks in a loudspeaker attached to a coil of wire around the iron. It was later determined that these jumps were caused by the movement of the magnetic domains in the iron, as the domain walls snap past defects in the crystal lattice. The energy lost in these dissipative events is responsible for the shape of the hysteresis curve of iron and other ferromagnets. This effect is widely used in research, and physics education as a simple experiment to demonstrate the reality of magnetic domains. He proposed the use of the phon as a unit of loudness. He also wrote a four volume textbook on electron tubes, Lehrbuch der Elektronenröhren, Elektronenröhren und ihre technischen Anwendungen, which was influential.
In 1920, he invented the Barkhausen–Kurz oscillator, It was the first vacuum tube oscillator that could operate at ultrahigh frequency, up to 300 MHz,