[The University of Texas at Austin: What starts here changes the world]
A A A

Physics Event · · ·

Hudspeth Memorial Lecture: Prof. Myriam Sarachik, City University of New York

Date and Time: Wednesday, September 18, 2013 at 4:15 PM (CDT)
Location: RLM 4.102

Hudspeth Memorial Lecture

Prof. Myriam Sarachik, City University of New York

"Quantum Tunneling and Magnetic Deflagration"

4:15pm, The John A. Wheeler Lecture Hall (RLM 4.102)

Coffee and cookies will be served at 4:00pm in RLM 4.102

Abstract:

Composed of a large ((~Avogadro’s) number of identical magnetic molecules of sizable spin (typically S~10) arranged on a regular lattice, crystals of molecular magnets are ideal laboratories for the study of nano-magnetism at the border between the classical and quantum regimes. Using Mn12-acetate as a prototypical example, and with the help of animations, we will take a quick tour of some fascinating physical processes that have found expression in these materials: “macroscopic” quantum tunneling of the magnetization, Berry phase interference, an abrupt transition between thermally-assisted and ground state tunneling…… The magnetization exhibits hysteresis at low temperatures in response to a magnetic field applied along the crystal easy axis, exhibiting a series of steps due to the reversal of the spin magnetic moment by quantum tunneling at specific “resonant” values of the magnetic field. An abrupt reversal of the magnetic moment of the entire sample can occur instead in the form of a magnetic avalanche in a process that is analogous to chemical deflagration (aka chemical combustion). In sufficiently high bias field, the Zeeman energy released by the reversing spins as they relax toward equilibrium leads to a dynamical instability that ignites rapid self-sustained relaxation along a deflagration front that propagates throughout the crystal at a constant subsonic speed. Recent experiments will be shown in which a trigger heat pulse and transverse and longitudinal magnetic fields were used to study and control the crossover between thermally driven magnetic relaxation and self-sustained magnetic deflagration, akin to a self-sustaining fire that spreads through the forest.

Upcoming
Events
September 16 14:00 RLM 7.104
Constraints on Chiral Operators in N=2 SCFTs and Implications for Theory Space
September 17 12:00 RLM 8.136
Topics of interest to physicists and mathematicians
September 17 16:15 The John A. Wheeler Lecture Hall (RLM 4.102)
Imaging the Electronic Properties of Graphene
September 18 11:00 RLM 11.204
Determining X-Ray Spectra of Radiographic Sources with a Compton Spectrometer
September 18 12:30 RLM 9.222
Members of the Theory Group discuss their work
September 18 12:30 RLM 11.204
Imaging and Spectroscopy of Graphene Heterostructures
September 18 14:00 RLM 13.202
Imaging Nanoscale Emergent Properties in Complex Oxides with Microwave Impedance Microscopy
September 19 16:00 RLM 5.104
Complex Nature of a 'Simple' Molecule
September 23 17:00 RLM 7.104
The Alice Experiment at the LHC -- A Little Big Bang!
September 24 16:15 The John A. Wheeler Lecture Hall (RLM 4.102)
The Question of Mass in Newton's Law of Gravity
September 25 12:30 RLM 11.204
title tbd
September 29 13:00 RLM 11.204
Rheology of suspensions and emulsions
September 30 09:00 RLM 13.202
Microwave Impedance Microscope Study of Two Dimensional Material Electrical Properties
September 30 17:00 RLM 7.104
Understanding the Higgs Boson with the Large Hadron Collider!
October 1 16:15 The John A. Wheeler Lecture Hall (RLM 4.102)
title tba
October 1 16:15 The John A. Wheeler Lecture Hall (RLM 4.102)
title tbd