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Research Interests
My principal research interests are in magnetic materials. In
particular, I am interested in the relationship between unconventional
superconductivity and magnetism, and magnetism in geometrically frustrated
materials. Much of my research thus far has involved the muon spin relaxation
and neutron scattering techniques at various facilities throughout North America
and the world, and I am also working on synthesis and basic characterization of
these materials..
My thesis research,
with Tomo
Uemura at Columbia University
explored magnetism in doped compounds of the Sr2RuO4 and FeAs-based
superconducting systems.
Currently I am an Assistant Professor in the
Physics Department at Villanova University, starting in Fall 2011. Prior to that
I worked as a Research Associate for the National
Research Council of Canada, working with Zahra
Yamani at the Canadian Neutron
Beam Centre, and Bruce
Gaulin at McMaster
University.
Selected Publications
J. P. Carlo et al. "New Magnetic
Phase Diagram of (Sr,Ca)2RuO4."
Nature
Materials 11, 323 (2012).
I. M. Gat-Malureanu
et al. "Muon spin relaxation and susceptibility measurements of an
itinerant-electron system Sr1-xCaxRuO3: quantum
evolution from ferromagnet to paramagnet."
Physical Review B
84, 224415 (2011).
J. P. Carlo et al. "Triplet
and in-gap magnetic states in the ground state of the quantum frustrated fcc
antiferromagnet Ba2YMoO6."
Physical Review B 84,
100404(R) (2011).
arXiv link.
H. Nojiri et al.
"Elucidating High Field Phases of the Multiferroic MnWO4 with
a Pulsed Magnetic Field and Time of Flight Neutron Laue Diffraction." Physical
Review Letters 106, 237202
(2011).
ORNL news item about this work.
J. Munevar et al.
"Static magnetic order of Sr4A2O6Fe2As2 (A
= Sc and V) revealed by Mossbauer and muon spin relaxation spectroscopies." Physical
Review B 84, 024527 (2011). arXiv
link
V. A. Blagojevic et
al. "Magnetic phase transition in V2O3nanocrystals." Physical
Review B 82, 094453 (2010).
arXiv
link
S. R. Dunsiger et al.
"Spatially homogeneous ferromagnetism of (Ga,Mn)As." Nature
Materials 9, 299 (2010).
J. P. Carlo et al.
"Static Magnetic Order and Superfluid Density of RFeAs(O,F) (R=La,Nd,Ce) and
LaFePO Studied by Muon Spin Relaxation: Unusual Similarities with the Behavior
of Cuprate Superconductors." Physical
Review Letters 102, 087001
(2009).
Y. J. Uemura et al.
"Phase Separation and Supression of Critical Dynamics at Quantum Transitions of
Itinerant Magnets: MnSi and (Sr1-xCax)RuO3." Nature
Physics 3, 29-35 (2007). arXiv
link.
PDF from Columbia CISE.
Recent Talks & Presentations
You can find several presentations that I have given here:
Villanova University Physics/Astronomy Debate,
January 2012, Villanova, PA
Adventures in Crystal Growth.
Canadian Neutron Beam Centre seminar, January 2011, Chalk River, ON
Studies of Magnetism in Ca2-xSrxRuO4 &
Sr2Ru1-yTiyO4.
2010 CIFAR Quantum Materials Main Meeting, May 2010, Montreal, QC (poster)
Outside Activities
For a little over 20 years I have been an
amateur astronomer.
I have two homemade telescopes - a 6" f/8 equatorial reflector and a 10" f/6.4
motorized Dobsonian - and two store-bought telescopes. I have been a member of
Amateur Astronomers, Inc. in New Jersey
since the early 1990's, where I was a Qualified Observer on the 24"
E. T. Pearson telescope,
and was the editor of the club's monthly newsletter,
The Asterism, for
six years. I frequently travel out to dark-sky sites such as
Cherry Springs State Park to observe, and have given a number of
astronomy-related lectures for fellow amateurs as well as the general public.
Here are several astronomy-related talks I have given over the last few years:
Radio Astronomy: Listening to the Sky (for
the Renfrew County Amateur Radio Club, January 2011)
Is Anyone Out There? Solving the Drake Equation
(May 2008)
What Happened to Pluto? (late 2006)
A few more talks on the "lighter side:"
Famous Last Words (of Scientists and Engineers)
Guide to Understanding
Scientific Papers (not my creation, but culled from collections on the
Interwebs....)
Practical Guide to Using a Slide Rule
I have been an FCC-licensed
amateur radio operator since 1994 (Amateur Extra class, call sign N2ZLQ). I
am a Volunteer Examiner (VE)
with ARRL-VEC and have assisted with numerous licensing exam sessions with
the Columbia University Amateur Radio Club's
VE Team. From 2006
through 2009 I was involved with the New York
City Amateur Radio Emergency Service (ARES), which provides public service
radio communications for large events such as marathons and parades, as well as
emergency communications in disasters. While in Canada, I was active with the
Renfrew County Amateur Radio Club, and their
ARES group as
well.
From 2006 through 2009, I was a New York State-certified Emergency Medical
Technician, and served as a volunteer EMT, dispatcher and training officer with
the Throggs Neck Volunteer Ambulance Corps in the Bronx, NY.
I have also recently been researching my
family history, which leads back to Colonial America, Italy, Germany,
England, France and Ireland, among other places. I am descended from
Benedict
Arnold (1615-1678), one of the first governors of Rhode Island, and am a
cousin to his much more famous (or is it infamous... depends on who you ask!)
great-grandson by the
same name. My great-great-great-grandfather Zimron Merriam fought in the
American Civil War and was held as a prisoner of war at the infamous
Andersonville prison; I have ancestors on both sides of the American
Revolution as well (including a few Loyalists who fled to Canada after the war,
only to return several decades later to upstate New York). On my father's side,
my great-grandfather Rocco Carlo narrowly escaped death in the
December 1908
Messina / Reggio Calabria earthquake, after which he came to the United
States to start a new life. I've traced another line of my family back to a
Thomas
B. Wielher, born in 819 AD in England; he is the patriarch of a long line of
Wielhers (later changed to Wheeler, my mother's maiden name), and if my math is
correct, my great36-grandfather.
Useful Neutron Scattering Stuff
Here are a few convenient calculators / tables I've generated in Microsoft Excel
for designing neutron experiments. They haven't been thoroughly checked for
bugs, just enough for my own use, so I provide them "as-is." Please contact me
with any questions, and I hope you find them helpful!
Calculate the positions of Aluminum reflections
Gives positions of aluminum peaks in |Q| and in scattering angle for several
standard pyrolytic graphite (PG) wavelengths. Also includes values for lambda/2
and lambda/3 harmonics. Useful for determining whether that curious signal is
coming from your sample holder...
Neutron flux vs. wavelength
for a reactor source
Plots relative neutron flux as a function of wavelength given a moderator / cold
source temperature. Assumes a purely Maxwellian distribution.
Calculate nuclear structure factor
for a given reflection
Input the atoms in your structure, and the (h,k,l) values for reflections of
interest, and this pops out the nuclear structure factors for those reflections.
It's probably easier to use something like PowderCell, but this is a good way to
check your results.
Magnetic scattering
calculator
Input a gaussian approximation to a magnetic form factor of interest, the
location (h,k,l) of the putative magnetic Bragg reflection, and the structure
factor and observed intensity of a reference nuclear reflection, and this
calculator tells you Imag/Inuc. It's not bulletproof, but nice to mess around
with if you want to estimate whether a magnetic peak will be observable.
Inelastic scattering
feasibility calculator
For a triple-axis instrument, input your instrument factors (wavelength, angle
limitations, etc.) and this calculator will tell you whether a given (Q,E)
position is achievable with those settings. Useful for planning an experiment.
Triple-axis inelastic
scattering accessible regions (fixed E_final)
Input instrument details for a triple-axis instrument (assuming a fixed final
energy), and this calculator outputs a graph of the accessible region of (Q,E)
space accessible with those settings.
Triple-axis inelastic scattering
accessible regions (fixed E_initial)
Same as previous, but done assuming a fixed initial energy. Also useful for TOF
instruments.
Useful Links
List
of CNBC spectrometers at Chalk River
Lectures from 2011 CNBC Neutron
Scattering Summer School
Lectures from 2009 CNBC
Neutron Scattering Summer School.
CNBC
Spectrometer Book
Table of Nuclides
Magnetic Neutron
Scattering Form Factors
IUCr International Tables for
Crystallography
Neutron scattering
lengths and cross-sections
Information for
Visitors to Deep River (from Lachlan Cranswick)
TRIUMF CMMS Page (access to TRIUMF schedule and muSR
data)
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