9 research outputs found
Theory-guided investigation on magnetic evolution of MnPtPdP and discovery of anti-CeCoIn-type ferromagnetic MnPdP
We report the magnetic changes from canted antiferromagnetic to ferromagnetic
orderings in anti-115-type MnPtPdP ( = 1, 2, 2.5, 3, 4, and 5)
and the discovery of a new rare-earth-free ferromagnet, MnPdP by both
theoretical prediction and experimental investigation. The family compounds
were synthesized using high temperature solid state method and characterized to
crystalize in the anti-CeCoIn type with the space group P4/mmm exhibiting a
two-dimensional layered structural feature. The magnetic property measurements
indicate that the compounds ordered from canted A-type antiferromagnet in
MnPtP to ferromagnet above the room temperature with varying degrees of
coercivity and magnetic moments in MnPdP by reducing the spin orbital
coupling. The results of the MnPtPdP have been analyzed in
comparison to the other candidates of the 151 family of Mn(Pt/Pd)(P/As) to
understand the complex structure-magnetism relationships
High Temperature Ferromagnetism in CrPtP
We present the growth and basic magnetic and transport properties of
CrPtP. We show that single crystals can readily be grown from a
high-temperature solution created by adding dilute quantities of Cr to Pt-P
based melts. Like other 1-5-1 compounds, CrPtP adopts a
tetragonal P4/mmm structure composed face-sharing CrPt like slabs that are
broken up along the c-axis by sheets of P atoms. EDS and X-ray diffraction
measurements both suggest CrPtP has mixed occupancy between Cr
and Pt atoms, similar to what is found in the closely related compound
CrPt, giving real compositions of CrPtP (x = 0.5). We
report that CrPtP orders ferromagnetically at T = 464.5 K
with a saturated moment of 2.1 /Cr at 1.8 K. Likely
owing to the strong spin-orbit coupling associated with the large quantity of
high Z Pt atoms, CrPtP has exceptionally strong planar
anisotropy with estimated anisotropy fields of 345 kOe and 220 kOe at 1.8 K and
300 K respectively. The resistance of CrPtP has a metallic
temperature dependence with relatively weak magnetoresistance. Electronic band
structure calculations show that CrPtP has a large peak in the density of
states near the Fermi level which is split into spin majority and minority
bands in the ferromagnetic state. Furthermore, the calculations suggest
substantial hybridization between Cr-3d and Pt-5d states near the Fermi level,
in agreement with the experimentally measured anisotropy
Continuous spin excitations in the three-dimensional frustrated magnet K2Ni2(SO4)3
Continuous spin excitations are widely recognized as one of the hallmarks of
novel spin states in quantum magnets, such as quantum spin liquids (QSLs).
Here, we report the observation of such kind of excitations in K2Ni2(SO4)3,
which consists of two sets of intersected spin-1 Ni2+ trillium lattices. Our
inelastic neutron scattering measurement on single crystals clearly shows a
dominant excitation continuum, which exhibits a distinct temperature-dependent
behavior from that of spin waves, and is rooted in strong quantum spin
fluctuations. Further using the self-consistent-gaussian-approximation method,
we determined the fourth- and fifth-nearest neighbor exchange interactions are
dominant. These two bonds together form a unique three-dimensional network of
corner-sharing tetrahedra, which we name as ''hyper-trillium'' lattice. Our
results provide direct evidence for the existence of QSL features in
K2Ni2(SO4)3 and highlight the potential for the hyper-trillium lattice to host
frustrated quantum magnetism.Comment: 6 pages and 5 figures, plus several pages of supplemental material,
comments are welcom
Mn(PtPd)P: Isovalent Tuning of Mn Sublattice Magnetic Order
We report the growth and characterization of MnPdP, a ferromagnet with
T 295 K, and conduct a substitutional study with its
antiferromagnetic analogue MnPtP. We grow single crystals of MnPdP and
Mn(PtPd)P by adding Mn into (PtPd)-P based melts.
All compounds in the family adopt the layered anti-CeCoIn structure with
space group P4/mmm, and EDS and XRD results indicate that MnPtP and
MnPdP form a solid solution. Based on magnetization and resistance data, we
construct a T-x phase diagram for Mn(PtPd)P and demonstrate the
antiferromagnetic order found in MnPtP is extraordinarily sensitive to Pd
substitution. At low Pd fractions (x 0.010), the single antiferromagnetic
transition in pure MnPtP splits into a higher temperature ferromagnetic
transition followed on cooling by a lower temperature ferromagnetic to
antiferromagnetic transition and then by a re-entrant antiferromagnetic to
ferromagnetic transition at lower temperatures. The antiferromagnetic region
makes up a bubble that persists to x 0.009 for T 150 K,
with all samples x 0.009 recovering their initial ferromagnetic state with
further cooling to base temperature. Over the same low x range we find a
non-monotonic change in the room temperature unit cell volume, further
suggesting that pure MnPtP is close to an instability. Once x 0.010,
Mn(PtPd)P undergoes a single ferromagnetic transition. The
Curie temperature increases rapidly with x, rising from T 197 K
at x = 0.013 to a maximum of T 312 K for x 0.62, and
then falls back to T 295 K for pure MnPdP (x = 1). Given that
Pt and Pd are isoelectronic, this work raises questions as to the origin of the
extreme sensitivity of the magnetic ground state in MnPtP upon introducing
Pd
Theoretical investigations of hydrogen absorption in the A15 intermetallics Ti3Sb and Ti3Ir
Ti3Sb and Ti3Ir adopt the A15 (Cr3Si type) structure and are reported to incorporate hydrogen atoms to an extent, respectively, of Ti3SbH∼3 and Ti3IrH3.8. First-principles electronic structure calculations were performed to identify factors contributing to the difference in maximum hydrogen composition for these two intermetallic compounds. Relative energies and changes in energy densities of states and crystal orbital Hamilton populations upon H insertion in the intermetallic compounds were examined. In both compounds, hydrogen atoms are attracted to [Ti4] tetrahedral interstitial sites over any others. The natures of metal-hydrogen and metalloid-hydrogen bonding and the effects of hydrogen insertion on metal-metal and metal-metalloid bonding have an influence on the maximum hydrogen contents for Ti3Sb and Ti3Ir.This article is published as Miller, Gordon J., Ranuri S. Dissanayaka Mudiyanselage, and Weiwei Xie. "Theoretical investigations of hydrogen absorption in the A15 intermetallics Ti3Sb and Ti3Ir." Zeitschrift für Naturforschung B 76, no. 10-12 (2021): 819-826.
DOI: 10.1515/znb-2021-0137
Copyright 2021 Gordon J. Miller et al.
Attribution 4.0 International (CC BY 4.0)
Posted with permission
New Tetragonal ReGa5(M) (M = Sn, Pb, Bi) Single Crystals Grown from Delicate Electrons Changing
Single crystals of the new Ga-rich phases ReGa~5(Sn), ReGa~5(Pb) and ReGa~5(Bi) were successfully obtained from the flux method. The new tetragonal phases crystallize in the space group P4/mnc (No. 128) with vertex-sharing capped Re2@Ga14 oblong chains. Vacancies were discovered on the Ga4 and Ga5 sites, which can be understood as the direct inclusion of elemental Sn, Pb and Bi into the structure. Heat capacity measurements were performed on all three compounds resulting in a small anomaly which resembles the superconductivity transition temperature from the impurity ReGa5 phase. The three compounds were not superconducting above 1.85 K. Subsequently, electronic structure calculations revealed a high density of states around the Fermi level, as well as non-bonding interactions that likely indicate the stability of these new phases
LiYbSe2: Frustrated Magnetism in a New Pyrochlore Lattice
Three-dimensionally (3D) frustrated magnets generally exist in the magnetic
diamond and pyrochlore lattices, in which quantum fluctuations suppress
magnetic orders and generate highly entangled ground states (GS). LiYbSe2 in a
previously unreported pyrochlore lattice was discovered from LiCl flux growth.
Distinct from the quantum spin liquid (QSL) candidate NaYbSe2 hosting a perfect
triangular lattice of Yb3+, LiYbSe2 crystallizes in the cubic pyrochlore
structure with space group Fd-3m (No. 227). The Yb3+ ions in LiYbSe2 are
arranged on a network of corner-sharing tetrahedra, which is particularly
susceptible to geometrical frustration. According to our temperature-dependent
magnetic susceptibility measurements, the dominant antiferromagnetic
interaction in LiYbSe2 is expected to appear around 8 K. However, no long-range
magnetic order is detected in thermomagnetic measurements above 70 mK. Specific
heat measurements also show magnetic correlations shifting with applied
magnetic field with a degree of missing entropy that may be related to the
slight mixture of Yb3+ on the Li site. Such magnetic frustration of Yb3+ is
rare in pyrochlore structures. Thus, LiYbSe2 shows promises in intrinsically
realizing disordered quantum states like QSL in pyrochlore structures
High Temperature Ferromagnetism in Cr1+xPt5−xP
We present the growth and basic magnetic and transport properties of Cr1+xPt5−xP. We show that single crystals can readily be grown from a high-temperature solution created by adding dilute quantities of Cr to Pt-P based melts. Like other 1-5-1 compounds, Cr1+xPt5−xP adopts a tetragonal P4/mmm structure composed face-sharing CrPt3 like slabs that are broken up along the c-axis by sheets of P atoms. EDS and X-ray diffraction measurements both suggest Cr1+xPt5−xP has mixed occupancy between Cr and Pt atoms, similar to what is found in the closely related compound CrPt3, giving real compositions of Cr1.5Pt4.5P (x = 0.5). We report that Cr1.5Pt4.5P orders ferromagnetically at TC = 464.5 K with a saturated moment of ≈ 2.1 μB/Cr at 1.8 K. Likely owing to the strong spin-orbit coupling associated with the large quantity of high Z Pt atoms, Cr1.5Pt4.5P has exceptionally strong planar anisotropy with estimated anisotropy fields of 345 kOe and 220 kOe at 1.8 K and 300 K respectively. The resistance of Cr1.5Pt4.5P has a metallic temperature dependence with relatively weak magnetoresistance. Electronic band structure calculations show that CrPt5P has a large peak in the density of states near the Fermi level which is split into spin majority and minority bands in the ferromagnetic state. Furthermore, the calculations suggest substantial hybridization between Cr-3d and Pt-5d states near the Fermi level, in agreement with the experimentally measured anisotropy.This article is published as Slade, Tyler J., Nao Furukawa, Tanner R. Smith, Juan Schmidt, Ranuri S. Dissanayaka Mudiyanselage, Lin-Lin Wang, Weiwei Xie, Sergey L. Bud'ko, and Paul C. Canfield. "High-temperature ferromagnetism in Cr 1+ x Pt 5− x P." Physical Review Materials 7, no. 2 (2023): 024410.
DOI: 10.1103/PhysRevMaterials.7.024410.
Copyright 2023 American Physical Society.
Posted with permission.
DOE Contract Number(s): AC02-07CH11358; NSF-DMR-205328
Mn(Pt1−xPdx)5P: Isovalent Tuning of Mn Sublattice Magnetic Order
We report the growth and characterization of MnPd5P, a rare-earth-free ferromagnet, with TC approximate to 295 K and planar anisotropy, and conduct a substitutional study with its antiferromagnetic analog MnPt5P. All compounds in the family adopt the layered anti-CeCoIn5-type structure with the space group P4/mmm, and EDS and x-ray diffraction results indicate that MnPt5P and MnPd5P form a complete solid solution. Based on measurements of the temperature-and field-dependent magnetization and resistance, we construct a temperature -composition (T -x) phase diagram for Mn(Pt1-xPdx )5P and demonstrate that the essentially antiferromagnetic order found in MnPt5P is extraordinarily sensitive to Pd substitution. At low Pd fractions (x 0.010, Mn(Pt1-xPdx )5P undergoes a only single transition into the ferromagnetic phase. The Curie temperature initially increases rapidly with x, rising from TC approximate to 197 K at x = 0.013 to a maximum of TC approximate to 312 K for x approximate to 0.62, and then falling back to TC approximate to 295 K for pure MnPd5P (x = 1.00). Given that Pt and Pd are isoelectronic, this work raises questions as to the origin of the extreme sensitivity of the magnetic ground state and the nature of the re-entrant ferromagnetism at dilute Pd levels.This article is published as Slade, Tyler J., Ranuri S. Dissanayaka Mudiyanselage, Nao Furukawa, Tanner R. Smith, Juan Schmidt, Lin-Lin Wang, Chang-Jong Kang et al. "Mn (Pt 1− x Pd x) 5 P: Isovalent tuning of Mn-sublattice magnetic order." Physical Review B 107, no. 13 (2023): 134429.
DOI: 10.1103/PhysRevB.107.134429.
Copyright 2023 American Physical Society.
Posted with permission.
DOE Contract Number(s): AC02-07CH11358; FOA-0001276; NSF-DMR-2053287; DMR-1644779; 2022R1C1C1008200