My principal research interests are in strongly correlated oxide materials, particularly magnetic and structural properties. I maintain specific interests in the relationship between unconventional superconductivity and magnetism, magnetism in geometrically frustrated
materials, and structural aspects of bulk perovskite 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. At Villanova I have established a sample
synthesis laboratory, containing several furnaces for synthesis of bulk oxide specimens, and a Siemens D500 powder diffractometer for structural characterization.
My thesis research,
Uemura at Columbia University
explored magnetism in doped compounds of the Sr2RuO4 and FeAs-based
Currently I am an Assistant Professor in the Physics Department at Villanova University. 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
J. J. Wagman et al. "Neutron
scattering studies of spin-phonon hybridization and superconducting spin
gaps in the high-temperature superconductor La2-x(Sr,Ba)xCuO4.
Physical Review B 93, 094416 (2016). (ArXiv
B. J. Chen et al.
"(Sr,Na)(Zn,Mn)2As2: A diluted ferromagnetic
semiconductor with the hexagonal CaAl2Si2 type
Physical Review B 90, 155202 (2014).
K. Zhao et al.
"(Ca,Na)(Zn,Mn)2As2: A new spin and charge doping
decoupled diluted ferromagnetic semiconductor."
Journal of Applied Physics 116, 163906 (2014).
C. M. Thompson et al. "Long-Range Magnetic Order in the 5d2 Double Perovskite Ba2CaOsO6: Comparison with Spin-Disordered Ba2YReO6."
Physics: Condensed Matter 26, 306003 (2014). (ArXiv link.)
J. P. Carlo et al. "Spin gap and the nature of the 4d3 magnetic ground state in the frustrated fcc antiferromagnet Ba2YRuO6."
Physical Review B 88, 024418 (2013). (ArXiv link.)
J. J. Wagman et al. "Two-dimensional incommensurate and three-dimensional commensurate magnetic order and fluctuations in La2-xBaxCuO4"
Physical Review B 88, 014412 (2013). (ArXiv link.)
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
Physical Review B 84,
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
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
V. A. Blagojevic et
al. "Magnetic phase transition in V2O3nanocrystals." Physical
Review B 82, 094453 (2010).
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
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
Recent Talks & Presentations
You can find several presentations that I have given here:
Structural and Magnetic Phase Coexistence in Oxygen Deficient
Perovskites (Sr,Ca)FeO2.5+d. March 2016, American
Physical Society March Meeting, Baltimore, MD. (conference poster)
Geometric Magnetic Frustration in Li3Mg2OsO6
Studied with Muon Spin Relaxation.
March 2016, American Physical Society
March Meeting, Baltimore, MD. (conference talk)
Long range magnetic order in
spin-orbit-coupled double perovskites Ba2YRuO6 and Ba2CaOsO6
probed with neutron scattering and muon spin relaxation. (abstract)
July 2014, International Conference on Highly Frustrated Magnetism (HFM
2014), Cambridge, UK. (conference poster)
Long range magnetic order in
spin-orbit-coupled double perovskites Ba2YRuO6 and
Ba2CaOsO6 probed with neutron scattering and muon
June 2014, American Conference on Neutron Scattering (ACNS 2014),
Knoxville, TN. (conference talk)
Magnetic Frustration in Double Perovskite Oxides A2BB'O6
June 2014, Oxides for Energy Meeting, Philadelphia, PA. (invited talk)
St. Joseph's University Physics Seminar, February 2014, Philadelphia, PA
(invited talk, presentation for undergraduates)
Probing magnetism in the
geometrically frustrated antiferromagnet Ba2YMoO6
using inelastic neutron scattering.
Seminar given at the Joint Institute for Neutron Sciences (JINS), Oak
Ridge National Laboratory, and as a Condensed Matter Physics seminar at
the University of Tennessee - Knoxville, April 2012.
Studies of Magnetism in Ca2-xSrxRuO4 &
2010 CIFAR Quantum Materials Main Meeting, May 2010, Montreal, QC (poster)
For a little over 20 years I have been an
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.
I currently serve as Secretary and newsletter editor of the
Delaware Valley Amateur Astronomers.
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
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
Practical Guide to Using a Slide Rule
I have been an FCC-licensed
amateur radio operator since 1994 (Amateur Extra class, call sign N2ZLQ),
and currently serve as President of the
Mid-Atlantic Amateur Radio Club (MARC). I
am a Volunteer Examiner (VE)
with ARRL-VEC, and in the past was active with ARES (Amateur Radio Emergency
Service), which provides radio communications for public service events and in
response to emergencies and disasters.
From 2006 through 2009, I was a New York State 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
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
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
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.
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.
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.
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
of CNBC spectrometers at Chalk River
Lectures from 2011 CNBC Neutron
Scattering Summer School
Lectures from 2009 CNBC
Neutron Scattering Summer School.
Table of Nuclides
Scattering Form Factors
IUCr International Tables for
lengths and cross-sections
Visitors to Deep River (from Lachlan Cranswick)
TRIUMF CMMS Page (access to TRIUMF schedule and muSR