high magnetic field suppression of afm in usb2_as presented
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LLNL-PRES-680527This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC
High-magnetic field suppression of antiferromagnetism in USb2
Ryan L. StillwellLawrence Livermore National Laboratory
Physical Phenomena at High Magnetic Fields VIIITallahassee, FL January 7, 2016
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Collaborators
Jason Jeffries
Lawrence Livermore National Laboratory
NIST Center for Neutron Research and U. MarylandNicholas Butch
I-Lin Liu
Marcelo Jaime
Neil Harrison
NHMFL-Pulsed Field Facility Los Alamos National Laboratory
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Outline
Why USb2?
Part One: Magnetostriction—AFM suppression seen via fiber Bragg
dilatometer
Part Two: Magnetization—AFM suppression confirmed via extraction
coil magnetometer
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Antiferromagnet below TN=202K— High energy scales involved
Highly anisotropic, quasi-two dimensional structure
U 5f-electrons are hybridized
Fermi surface reconstruction going from paramagnetic to antiferromagnetic phase
Introduction to USb2
D. Aoki et al., Phil. Mag. B, 80, 1517 (2000)
Paramagnetic
Antiferromagnetic
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D. Aoki et al., Phil. Mag. B, 80, 1517 (2000)
USb2 AFM unit cell is 2x the chemical unit cell
AFM unit cell
chemical unit cell
Paramagnetic
Antiferromagnetic
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Part One
Magnetostriction
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Fiber Bragg dilatometer avoids eddy current heating and enables measurements in pulsed fields
c-axis//H1 mm a-b plane//H
Had to stack 6 crystals
a) b) c)
d)
R. Daou et al., RSI, 81, 033909 (2010)M. Jaime et al., PNAS, 31, 12404 (2012)
A. Grockowiak, in preparation
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Thermal contraction along a-b plane confirms AFM transition at TN= 202K
TN
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USb2 does not show AFM transition in magnetostriction along the a-b plane
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vertical offset for clarity
USb2 shows AFM transition in magnetostriction along the c axis
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H-T phase diagram of AFM-PM transition observed via magnetostriction along the c axis
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What is the high-field magnetic structure?Is there a change from 2nd to 1st order at lower T?
vertical offset for clarity
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Part Two
Magnetization
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USb2 sample loading for extraction coil magnetometry
Sample with c-axis coming out of the picture
Sample is ~50μm thick100μm
Compensated coils for magnetization measurements
Sample outSample in
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USb2 extraction coil magnetometry clearly shows AFM transition
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USb2 phase diagram matches well between magnetostriction and magnetization
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Established first H-T phase diagram of USb2.
Magnetostriction and magnetization phase boundaries agree.
High-field, low-temperature magnetic state still unclear (ie. PM or canted-AFM) due to field limitation.
Quantum oscillations to see Fermi surface above Hc?
Experiment on UBi2 to see possible Fermi surface effects.
Conclusions and Future Work
Thank You!
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Quantitative analysis via corrected background gives magnetic moment smaller by ~0.8μB
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USb2 AFM transition in magnetostriction along the c axis downsweep
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High field magnetostriction along c-axis
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Structures of all UX2 compounds
D. Aoki et al., Phil. Mag. B, 80, 1517 (2000)
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