Brookhaven National Laboratory (BNL) researcher Ignace Jarrige shown with the sample used in the magnetic refrigeration experiment. Courtesy BNLFor more than 50 years, scientists around the world have attempted to understand the intriguing phenomena of the Kondo effect. When magnetic impurities are added to non-magnetic host materials, their properties display unexpected, anomalous behavior as a result of the Kondo effect. These dilute magnetic alloys, and their unusual behaviors are important tools for scientific research in topics such as ferromagnetism, superconductivity, and other solid-state phenomena. The Kondo effect provides insight into the electronic properties of a wide variety of materials and opens doors to new discoveries.
Dutch physicist and mathematician Wander Johannes de Haas and fellow researchers observed an unexpected rise in the resistivity of some gold samples at low temperatures in 1933. This was unusual because metals were expected to show a residual resistivity as their temperatures were reduced. Some thirty years later, American physicist Phil Anderson developed a microscopic model of how local magnetic moments form in metals with magnetic impurities. Then in 1964, Japanese theorist Jun Kondo finally was able to explain the scattering of electrons from a localized magnetic impurity. Kondo's key concept has continued to evolve through the decades.
In the era of today's nanoscience and nanotechnology, the Kondo effect can be studied with unprecedented control, using tools such as quantum-dot devices, tunneling microscopy, and x-ray scattering. A recent breakthrough in magnetic refrigeration is an example of current research related to the Kondo effect. A paper describing the team's results [1] was published in the journal Physical Review Letters [2]. This Department of Energy-affiliated journal article [3] is freely available to the public in DOE PAGESBeta [4], the DOE portal that makes scholarly scientific publications resulting from DOE research funding publicly accessible and searchable at no charge to users.
An overview of the Kondo effect and related research is provided in William Watson's latest white paper "In the OSTI Collections: The Kondo Effect [5]."