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Title: Quantum Coherence and Random Fields at Mesoscopic Scales

We seek to explore and exploit model, disordered and geometrically frustrated magnets where coherent spin clusters stably detach themselves from their surroundings, leading to extreme sensitivity to finite frequency excitations and the ability to encode information. Global changes in either the spin concentration or the quantum tunneling probability via the application of an external magnetic field can tune the relative weights of quantum entanglement and random field effects on the mesoscopic scale. These same parameters can be harnessed to manipulate domain wall dynamics in the ferromagnetic state, with technological possibilities for magnetic information storage. Finally, extensions from quantum ferromagnets to antiferromagnets promise new insights into the physics of quantum fluctuations and effective dimensional reduction. A combination of ac susceptometry, dc magnetometry, noise measurements, hole burning, non-linear Fano experiments, and neutron diffraction as functions of temperature, magnetic field, frequency, excitation amplitude, dipole concentration, and disorder address issues of stability, overlap, coherence, and control. We have been especially interested in probing the evolution of the local order in the progression from spin liquid to spin glass to long-range-ordered magnet.
Authors:
 [1]
  1. Univ. of Chicago, IL (United States)
Publication Date:
OSTI Identifier:
1240767
Report Number(s):
DOE-CHICAGO--45789
TRN: US1600675
DOE Contract Number:
FG02-99ER45789
Resource Type:
Technical Report
Research Org:
Univ. of Chicago, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; SPIN; NEUTRON DIFFRACTION; EXCITATION; RANDOMNESS; SPIN GLASS STATE; MAGNETIC FIELDS; DIPOLES; FLUCTUATIONS; INFORMATION; LIQUIDS; NONLINEAR PROBLEMS; QUANTUM ENTANGLEMENT; TEMPERATURE DEPENDENCE; TUNNEL EFFECT; AMPLITUDES; CONTROL; EVOLUTION; PROBABILITY; SENSITIVITY; STABILITY; STORAGE; WALLS; FERROMAGNETIC MATERIALS; DOMAIN STRUCTURE; FANO FACTOR; FREQUENCY DEPENDENCE