Heinrich Georg Barkhausen (2 December 1881 – 20 February 1956), born in

Bremen Bremen (Low German also: ''Breem'' or ''Bräm''), officially the City Municipality of Bremen (german: Stadtgemeinde Bremen, ), is the capital of the German state Free Hanseatic City of Bremen (''Freie Hansestadt Bremen''), a two-city-state consis ...

, was a German physicist. Growing up in a patrician Bremen family, he showed interest in natural sciences from an early age. He studied at the

Technical University of Munich The Technical University of Munich (TUM or TU Munich; german: Technische Universität München) is a public research university in Munich, Germany. It specializes in engineering, technology, medicine, and applied and natural sciences. Establis ...

(1901), TU Berlin (1902) and University of Munich (1903) and

Berlin Berlin ( , ) is the capital and largest city of Germany by both area and population. Its 3.7 million inhabitants make it the European Union's most populous city, according to population within city limits. One of Germany's sixteen constitue ...

before obtaining a doctorate at the

University of Göttingen The University of Göttingen, officially the Georg August University of Göttingen, (german: Georg-August-Universität Göttingen, known informally as Georgia Augusta) is a public research university in the city of Göttingen, Germany. Founded ...

in 1907. He became professor of electrical engineering at the

Technische Hochschule Dresden TU Dresden (for german: Technische Universität Dresden, abbreviated as TUD and often wrongly translated as "Dresden University of Technology") is a public research university, the largest institute of higher education in the city of Dresden, th ...

in 1911 at the age of 29, thus obtaining the world's first chair in this discipline. In 1919, he discovered the Barkhausen effect (named after him), which provided evidence for the magnetic domain theory of ferromagnetism. 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 wall A domain wall is a type of topological soliton that occurs whenever a discrete symmetry is spontaneously broken. Domain walls are also sometimes called kinks in analogy with closely related kink solution of the sine-Gordon model or models with pol ...

s snap past defects in the crystal lattice. The energy lost in these dissipative events is responsible for the shape of the

hysteresis Hysteresis is the dependence of the state of a system on its history. For example, a magnet may have more than one possible magnetic moment in a given magnetic field, depending on how the field changed in the past. Plots of a single component of ...

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. In 1920, he invented the Barkhausen–Kurz oscillator, with K. Kurz, the first

vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. The type kn ...

electronic oscillator An electronic oscillator is an electronic circuit that produces a periodic, oscillation, oscillating electronic signal, often a sine wave or a square wave or a triangle wave. Oscillation, Oscillators convert direct current (DC) from a power supp ...

to use electron transit-time effects. It was the first vacuum tube oscillator that could operate at ultrahigh frequency, up to 300 MHz, and inspired later

microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ran ...

transit-time tubes such as the klystron. In 1921 he derived the first mathematical conditions for

oscillation Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...

in electrical circuits, now called the Barkhausen stability criterion. They are widely used today in the design of

s and general feedback

amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost the v ...

circuits. In 1933 Barkhausen signed the '' Loyalty Oath of German Professors to Adolf Hitler and the National Socialist State''.

Publications

Four-volume textbook: ''Lehrbuch der Elektronenröhren, Elektronenröhren und ihre technischen Anwendungen''.

References

External links

* * {{DEFAULTSORT:Barkhausen, Heinrich 1881 births 1956 deaths 20th-century German physicists Technical University of Munich alumni 20th-century German inventors Members of the German Academy of Sciences at Berlin