Studies on Rare Earth Metals and Alloys under Extreme Conditions in Support of the Stockpile Stewardship ProgramFaculty and Staff:Yogesh K. VohraGopi SamudralaHPCAT StaffCurrent Graduate Students:Kaleb BurrageSeth IwanChristopher PerreaultUniversity of Alabama at BirminghamLos Alamos National Lab Collaborators:Blake Sturtevant and Jeffrey PigottLawrence Livermore National Lab Collaborators:Nenad Velisavljevic and Jason JeffriesOak Ridge National Laboratory Collaborators:Antonio M. dos Santos, Jamie Molaison, Reinhard Boehler

Grant No: DE-NA0003916

Current UAB Graduate Students in the SSAA Program

Chris Perreault – Intern at LANL Kaleb Burrage – Intern at SNL

Seth Iwan –New Graduate Student

Former Graduate Student at NNSA Labs

The following six graduate students were placed at DOE/NNSA Laboratories after graduation from the high pressure research lab at the University of Alabama at Birmingham (UAB):

Dr. Gary Neal Chesnut, Los Alamos National Laboratory

Dr. Kathryn Ham, Lawrence Livermore National Laboratory

Dr. Jeffrey Montgomery, Nevada National Security Site, Los Alamos

Dr. Jeremy Reed Patterson, Lawrence Livermore National Laboratory

Dr. Sarah Thomas, Nevada National Security Site, Los Alamos

Dr. Nenad Velisavljevic, LLNL/Director-HPCAT, Argonne National Laboratory

Introduction and Presentation Outline• Mission Statement: To develop enabling technologies and infrastructure for

providing accurate and simultaneous electrical, magnetic, structural, and melt data on rare earth metals and alloys under extreme conditions relevant to the stockpile stewardship program.

• Our overall effort at UAB, supported by NNSA-SSAA program, can be summed into three major areas

– Development of advanced experimental probes for extreme pressure-temperature (P-T) experiments on 4-f rare earth metals and alloys

• In particular main effort has been on the development of designer diamond anvils with embedded thermocouples, nanocrystalline and toroidal diamond anvils for use in diamond anvil cell experiments in the Terapascal (TPa) pressure range

– Neutron diffraction studies on magnetic ordering in rare earth metals at high pressures and low temperature

• Use of spallation neutron source with a large volume DAC for neutron diffraction – Establishing new collaborations with national laboratories and developing next

generation work force in the areas of NNSA laboratory needs

Cleanroom with Mask-less Microlithography @ UAB

Sputter Deposition of Metals on Diamond

Diamond Microfabrication Laboratory at UAB

Eight Probe Electrical Sensor

Magnetic Susceptibility

350 μm

NCD micro-anvil FIB Machining

Thermal properties measurements in a DAC

(a) Shows the image of a diamond anvil with anintegrated K-type thermocouple. The probe labeled 'C'is chromel(Ni90Cr10), and the probe labeled 'A' isalumel(Ni95Al2Mn2Si1). (b) Shows the culet region ofthe anvil where the thermocouple junction ofchromel-alumel is formed.

Type G thermocouple (W –W/Re alloy)fabricated on the culet of adiamond anvil.

50 µm

Challenges in Neutron Diffraction Studies of Magnetic Phase Transitions in Rare Earth Metals at High Pressures and Low Temperatures

Source: NIST Center for Neutrons Research

Spallation Neutrons and Pressure DiffractometerOak Ridge National Laboratory (ORNL)

Large Volume Diamond Anvil Cell for Neutron Diffraction

Magnetic Structure in Ho under High Pressures

Conical Ferromagnetic

Helical Antiferromagnetic

Incommensurate Antiferromagnetic Phase of Ho

Incommensurate Antiferromagnetic Phase of Ho

Ferromagnetic Transition in the dhcp Phase of Ho

X-ray Diffraction of Holmium at High-Pressures and Low-Temperatures – Absence of Magnetic Peak @ 3 Å

Magnetic Superlattice Formation In Holmium

Challenges in Generating High Pressure Static Compression Data on Rare Earths

• Static high pressure data on rare earth metals have been limited topressure up to 200 GPa using conventional beveled diamond anvils. Thisis due to high compressibility and low tensile strength of 120-160 MPa.

• Ultrahigh pressure was generated by a pair of toroidal diamond anvilsprepared by focused ion beam machining of diamond anvils. Rare earthmetal Holmium was compressed to a pressure of 300 GPa with toroidaldiamond anvil – which is a new milestone as earlier high pressure studieson rare earth metals have been limited to 200 GPa.

Machining of Toroidal Diamond Anvils by Focused Ion Beam Machining

SEM (a) Side-view of the starting beveled diamond anvil. (b) Top-view of the FIBmachined toroidal anvil with a central flat region of 16 microns and outer regions of 40and 65 microns in diameter. (c) Close-up side-view of the toroidal shape of the diamondanvil showing the groove depth of 2.6 microns.

The ion source of the FIB machine was a Ga beam held at 5 nAwith 30keV and beam size of 50 nm.

Equation of State of Holmium to 282 GPa

Run 1: Cu pressure marker; Run 2: Pt pressure markerEquation of State: Bulk Modulus (B0) = 29.1 ± 3.0 GPaPressure Derivative of Bulk Modulus (B’0) = 3.80 ± 0.1

Compression of Superhard Osmium Boride to 358 GPa(Platinum Pressure Marker)

Os2B3Bulk Modulus (B0) = 401 GPaPressure Derivative (B’0) = 3.95

Anisotropic Compression in Metal Borides(Osmium Boride to 358 GPa )

0.84

0.86

0.88

0.9

0.92

0.94

0.96

0.98

1

0 50 100 150 200 250 300 350 400

Os2B3

Rare Earth Metals under High Pressures and High Temperatures (Double-sided Laser Heating)Dysprosium, P =5.3 GPa and T = 300 K

Novel Phases of Rare Earth Metals under High Pressures and High TemperaturesDysprosium, P=30 GPa and T = 1540 K (Ortho Cmmm)

Research Milestones in 2019/Future Plans • Rare earth metal Holmium (Ho) has been studied at the Spallation

Neutron Source, Oak Ridge National Lab to 20 GPa and 10 K. NewFerromagnetic transitions were observed in the high pressure alpha-Samarium-type phase and the double hexagonal close packed phases ofHolmium

• Ultrahigh pressure was generated by a pair of toroidal diamondanvils prepared by focused ion beam machining of diamond anvils.Rare earth metal Holmium was compressed to a pressure of 300 GPawith toroidal diamond anvil (V/V0 = 0.33)

• High-pressure high-temperature studies on rare earth metals hasreveled novel high pressure phases. Progress in generating thermalequation of state of rare earth metals

• Tungsten-Tungsten Rhenium thermocouple were fabricated on top ofthe designer diamond anvils and being evaluated in a double-sidedlaser heating configuration at HPCAT

Peer Reviewed Publications (2019-2020)

(1) Christopher Perreault, Yogesh K. Vohra, Antonio M. dos Santos, Jamie J.Molaison & Reinhard Boehler, “Magnetic ordering in rare earth metaldysprosium revealed by neutron diffraction studies in a large-volumediamond anvil cell”, High Pressure Research 39, 588-597 (2019).https://doi.org/10.1080/08957959.2019.1688800

(2) Ryan L. Stillwell, Xiangfeng Wang, Limin Wang, Daniel J. Campbell,Johnpierre Paglione, Samuel T. Weir, Yogesh K. Vohra, and Jason R.Jeffries “Observation of two collapsed phases in CaRbFe4As4” Phys. Rev.B 100, 045152 (2019). https://link.aps.org/doi/10.1103/PhysRevB.100.045152

(3) D. VanGennep, T. A. Paul, C. W. Yerger, S. T. Weir, Y. K. Vohra, and J. J.Hamlin, “Possible pressure-induced topological quantum phase transitionin the nodal line semimetal ZrSiS”, Phys. Rev. B 99, 085204 (2019).https://doi.org/10.1103/PhysRevB.99.085204

(4) J. S. Pigott, N. Velisavljevic, E. K. Moss, D. Popov, C. Park, J. A. VanOrman, N. Draganic, Y. K. Vohra, and B. T. Sturtevant, “Room-temperaturecompression and equation of state of body-centered cubic zirconium”, J.Phys: Condens. Matter 32, 12LT02 (2020). https://doi.org/10.1088/1361-648X/ab5e6e