Magnetic exchange interactions
Superexchange, or Kramers–Anderson superexchange, is the strong (usually) antiferromagnetic coupling between two next-to-nearest neighbour cations through a non-magnetic anion. In this way, it differs from direct exchange, in which there is coupling between nearest neighbor cations not involving an intermediary anion. Superexchange is a result of the electrons having come from the same donor atom and being coupled with the receiving ions' spins. If the two next-to-nearest neighbor positive ions are connected at 90 degrees to the bridging non-magnetic anion, then the interaction can be a ferromagnetic interaction. Superexchange was proposed by Hendrik Kramers in 1934, when he noticed that in crystals like MnO, there are Mn atoms that interact with one another despite having nonmagnetic oxygen atoms between them. Phillip Anderson later refined Kramers' model in 1950. A set of semi-empirical rules were developed by John B. Goodenough and in the 1950s. These rules, now referred to as the Goodenough–Kanamori rules, have proven highly successful in rationalizing the magnetic properties of a wide range of materials on a qualitative level. They are based on the symmetry relations and electron occupancy of the overlapping atomic orbitals (assuming the localized , or valence-bond, model is more representative of the chemical bonding than is the delocalized, or , model). Essentially, the Pauli exclusion principle dictates that between two magnetic ions with half-occupied orbitals, which couple through an intermediary non-magnetic ion (e.g. O2−), the superexchange will be strongly anti-ferromagnetic while the coupling between an ion with a filled orbital and one with a half-filled orbital will be ferromagnetic. The coupling between an ion with either a half-filled or filled orbital and one with a vacant orbital can be either antiferromagnetic or ferromagnetic, but generally favors ferromagnetic. When multiple types of interactions are present simultaneously, the antiferromagnetic one is generally dominant, since it is independent of the intra-atomic exchange term. For simple cases, the Goodenough–Kanamori rules readily allow the prediction of the net magnetic exchange expected for the coupling between ions. Complications begin to arise in various situations: 1) when direct exchange and superexchange mechanisms compete with one another; 2) when the cation–anion–cation bond angle deviates away from 180°; 3) when the electron occupancy of the orbitals is non-static, or dynamical; and 4) when spin–orbit coupling becomes important. Double exchange is a related magnetic coupling interaction proposed by Clarence Zener to account for electrical transport properties. It differs from superexchange in the following manner: in superexchange, the occupancy of the d-shell of the two metal ions is the same or differs by two, and the electrons are localized. For other occupations (double exchange), the electrons are itinerant (delocalized); this results in the material displaying magnetic exchange coupling, as well as metallic conductivity. (Wikipedia).
Build Your Own Supercomputer 1 - About Supercomputers
Supercomputer Playlist: http://www.youtube.com/watch?v=13x90STvKnQ&list=PLQVvvaa0QuDf9IW-fe6No8SCw-aVnCfRi&feature=share Greetings and welcome to my "how to build your own supercomputer" tutorial series. In this video, the concept of supercomputers is introduced, their history, and the ba
From playlist Build your Own Supercomputer
How to compare turbocharger with supercharger. ✔
More details visit: http://www.techtrixinfo.com/ Comparison of Turbocharger and Supercharger. Related topics: Technical explained working of explanation repair maintenance automobile engineering mechanical details on cars vehicles technology technical the best worlds best perfect well ve
From playlist Turbochargers/ Superchargers
The Universe is always surprising us with how little we know about... the Universe. It's continuously presenting us with stuff we never imagined, or even thought possible. The search for extrasolar planets is a great example. Since we started, astronomers have turned up over a thousand
From playlist Planets and Moons
If you rotate a bowling ball, it looks the same even though it's been "transformed". We say that the bowling ball exhibits "rotational symmetry". The particles making up the universe exhibit related kinds of symmetries, in which the particles are transformed but the equations describing th
From playlist Science Unplugged: Supersymmetry
Microscopic Origin of couplings between spins in Mott insulators (Tutorial 2) by Karlo Penc
PROGRAM FRUSTRATED METALS AND INSULATORS (HYBRID) ORGANIZERS: Federico Becca (University of Trieste, Italy), Subhro Bhattacharjee (ICTS-TIFR, India), Yasir Iqbal (IIT Madras, India), Bella Lake (Helmholtz-Zentrum Berlin für Materialien und Energie, Germany), Yogesh Singh (IISER Mohali, In
From playlist FRUSTRATED METALS AND INSULATORS (HYBRID, 2022)
Proves the Principle of Superposition for linear, homogeneous odes. Join me on Coursera: Matrix Algebra for Engineers: https://www.coursera.org/learn/matrix-algebra-engineers Differential Equations for Engineers: https://www.coursera.org/learn/differential-equations-engineers Vector C
From playlist Differential Equations
Superannuation (1 of 3: Using Sequences to understand superannuation questions)
More resources available at www.misterwootube.com
From playlist Money Matters
Is there any evidence that supersymmetry exists, or is it purely theoretical?
Subscribe to our YouTube Channel for all the latest from World Science U. Visit our Website: http://www.worldscienceu.com/ Like us on Facebook: https://www.facebook.com/worldscienceu Follow us on Twitter: https://twitter.com/worldscienceu
From playlist Science Unplugged: Supersymmetry
The Quantum Phases of Matter V - Quasiparticle lifetime; Superexchange interactions - Subir Sachdev
Joint Course with TIFR and IAS Topic: The Quantum Phases of Matter V Speaker: Subir Sachdev Affiliation: Harvard University; Member, School of Natural Sciences, IAS Date: September 20, 2021
From playlist Joint Course with TIFR and IAS
Build Your Own Supercomputer 5 - Testing supercomputer process
Supercomputer Playlist: http://www.youtube.com/watch?v=13x90STvKnQ&list=PLQVvvaa0QuDf9IW-fe6No8SCw-aVnCfRi&feature=share In this part of how to build a supercomputer, we test the MPI and supercomputing technology on a single node. http://seaofbtc.com http://sentdex.com http://hkinsley.co
From playlist Build your Own Supercomputer
Further Superannuation (Worked Example of harder superannuation question)
More resources available at www.misterwootube.com
From playlist Money Matters
Microscopic Origin of couplings between spins in Mott insulators -1 & 2 (Tutorial) by Karlo Penc
PROGRAM FRUSTRATED METALS AND INSULATORS (HYBRID) ORGANIZERS: Federico Becca (University of Trieste, Italy), Subhro Bhattacharjee (ICTS-TIFR, India), Yasir Iqbal (IIT Madras, India), Bella Lake (Helmholtz-Zentrum Berlin für Materialien und Energie, Germany), Yogesh Singh (IISER Mohali, In
From playlist FRUSTRATED METALS AND INSULATORS (HYBRID, 2022)
The Most Extreme Explosion in the Universe
Go ‘beyond the nutshell’ at https://brilliant.org/nutshell by diving deeper into these topics and more with 20% off an annual subscription! This video was sponsored by Brilliant. Thanks a lot for the support! Sources & further reading: https://sites.google.com/view/sources-supernovadeath
From playlist The Existential Crisis Playlist