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# Yeong-Ah Soh <yeong-ah.soh@dartmouth.edu>
# requesting 6 days, at minimum=4 days
# beamline 34ID-E, Xray imaging of antiferromagnetic domains in Cr films
# instrument 34ID-E microbeam
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# top:/home/www/beamtime-requests/req01078.txt
# UNICAT Member Beam Time Request  #1078
# created Tue Dec 12 21:27:05 CST 2006
####################################################

apsrun:
	2007-01

beamline:
	34ID-E

collaboration:
	Yes

contact:
	yeong-ah.soh@dartmouth.edu

days:
	6

description:
	We recently conducted transport measurements on Cr films (thickness ranging from 18 to 350 nm), and we observe thermal hysterisis in both longitudinal and Hall resistivity.  We attribute the thermal hysteresis to quantization of SDW in thin films and evolution of antiferromagnetic domains as a function of temperature.  In order to understand the thermal hysteresis in resistivity, we propose to conduct xray scattering measurements to measure the temperature dependence of the strain wave associated with the spin density wave and the antiferromagnetic domains in our Cr films.  Due to the small thickness of our films, we believe that the spin density wave has a Q-vector pointing perpendicular to the film that is subject to boundary conditions imposed by the interfaces with air and substrate.  This results in the quantization of number of nodes in the spin density wave, and a thermal hysteresis in the number of nodes, which results in a kink in the first derivative of the longitudinal and Hall resistivity.   In addition to the above effect, a second type of thermal hysteresis is observed, which we believe is associated to the antiferromagnetic domain configuration being different during cool down vs. warm up.  The xray measurements will be significant since it will show whether antiferromagnetism and associated domains have a profound role in the transport properties, a subject that will likely spark a large amount of interest.  The first set of measurements will be to characterize the antiferromagnetic spin density wavevector Q as a function of temperature and measure the distribution of Q vectors.  The second set of experiments will require a submicron beam to spatially map the Q domain distribution as a function of temperature.  The questions to be answered are the following: Is the spin density wave commensurate or incommensurate?  Are all Q vectors populated equally or not?  Does the population change as a function of temperature?  What is the typical Q domain size?  Does it grow as the system is cooled down?

equipment_required:
	cryostat

experiment:
	Xray imaging of antiferromagnetic domains in Cr films

foreign_nationals:
	

hazards:
	None.

instrument:
	34ID-E microbeam

instrument_other:
	

minimumdays:
	4

name:
	Yeong-Ah Soh

nonmembers:
	

submit:
	Submit

unacceptable_dates:
	Feb 16-17.
Mar 4-9.

z34ID_change_undulator:
	no

z34ID_details:
	

z34ID_parasitic:
	no


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