Heinrich Georg Barkhausen (2 December 1881 – 20 February 1956), born in Bremen, 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 The Technical University of Berlin (official name both in English and german: link=no, Technische Universität Berlin, also known as TU Berlin and Berlin Institute of Technology) is a public research university located in Berlin, Germany. It wa ...

(1902) and

University of Munich The Ludwig Maximilian University of Munich (simply University of Munich or LMU; german: Ludwig-Maximilians-Universität München) is a public research university in Munich, Germany. It is Germany's sixth-oldest university in continuous operatio ...

(1903) and

Berlin Berlin ( , ) is the capital and List of cities in Germany by population, largest city of Germany by both area and population. Its 3.7 million inhabitants make it the European Union's List of cities in the European Union by population within ci ...

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 The Barkhausen effect is a name given to the noise in the magnetic output of a ferromagnet when the magnetizing force applied to it is changed. Discovered by German physicist Heinrich Barkhausen in 1919, it is caused by rapid changes of size o ...

(named after him), which provided evidence for the

magnetic domain A magnetic domain is a region within a magnetic material in which the magnetization is in a uniform direction. This means that the individual magnetic moments of the atoms are aligned with one another and they point in the same direction. When c ...

theory of ferromagnetism. When the magnetic field through a piece of

ferromagnetic material Ferromagnetism is a property of certain materials (such as iron) which results in a large observed magnetic permeability, and in many cases a large magnetic coercivity allowing the material to form a permanent magnet. Ferromagnetic materials ...

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 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 potential difference has been applied. The type known as ...

electronic oscillator to use electron transit-time effects. It was the first vacuum tube oscillator that could operate at

ultrahigh frequency Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (o ...

, 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 ra ...

transit-time tubes such as the

klystron A klystron is a specialized linear-beam vacuum tube, invented in 1937 by American electrical engineers Russell and Sigurd Varian,Pond, Norman H. "The Tube Guys". Russ Cochran, 2008 p.31-40 which is used as an amplifier for high radio frequen ...

. 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 In electronics, the Barkhausen stability criterion is a mathematical condition to determine when a linear electronic circuit will oscillate. It was put forth in 1921 by German physicist Heinrich Georg Barkhausen (1881–1956). It is widely u ...

. They are widely used today in the design of electronic oscillators 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 t ...

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