Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Ab-Initio Study of Magnetically Intercalated Platinum Diselenide: The Impact of Platinum Vacancies
We study the magnetic properties of platinum diselenide (PtSe2) intercalated with Ti, V, Cr, and Mn, using first-principle density functional theory (DFT) calculations and Monte Carlo (MC) simulations. First, we present the equilibrium position of intercalants in PtSe2 obtained from the DFT calculations. Next, we present the magnetic groundstates for each of the intercalants in PtSe2 along with their critical temperature. We show that Ti intercalants result in an in-plane AFM and out-of-plane FM groundstate, whereas Mn intercalant results in in-plane FM and out-of-plane AFM. V intercalants result in an FM groundstate both in the in-plane and the out-of-plane direction, whereas Cr results in an AFM groundstate both in the in-plane and the out-of-plane direction. We find a critical temperature of <0.01 K, 111 K, 133 K, and 68 K for Ti, V, Cr, and Mn intercalants at a 7.5% intercalation, respectively. In the presence of Pt vacancies, we obtain critical temperatures of 63 K, 32 K, 221 K, and 45 K for Ti, V, Cr, and Mn-intercalated PtSe2, respectively. We show that Pt vacancies can change the magnetic groundstate as well as the critical temperature of intercalated PtSe2, suggesting that the magnetic groundstate in intercalated PtSe2 can be controlled via defect engineering.  more » « less
Award ID(s):
1917025
PAR ID:
10338130
Author(s) / Creator(s):
; ; ; ;
Date Published:
Journal Name:
Materials
Volume:
14
Issue:
15
ISSN:
1996-1944
Page Range / eLocation ID:
4167
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; (, 2D Materials)
    Abstract Transition metal dichalcogenides, intercalated with transition metals, are studied for their potential applications as dilute magnetic semiconductors. We investigate the magnetic properties of WSe 2 doped with third-row transition metals (Co, Cr, Fe, Mn, Ti and V). Using density functional theory in combination with Monte Carlo simulations, we obtain an estimate of the Curie or Néel temperature. We find that the magnetic ordering is highly dependent on the dopant type. While Ti and Cr-doped WSe 2 have a ferromagnetic ground state, V, Mn, Fe and Co-doped WSe 2 are antiferromagnetic in their ground state. For Fe doped WSe 2 , we find a high Curie-temperature of 327 K. In the case of V-doped WSe 2 , we find that there are two distinct magnetic phase transitions, originating from a frustrated in-plane antiferromagnetic exchange interaction and a ferromagnetic out-of-plane interaction. We calculate the formation energy and reveal that, in contrast to earlier reports, the formation energy is positive for the intercalated systems studied here. We also show that in the presence of W-vacancies, it becomes favorable for Ti, Fe, and Co to intercalate in WSe 2 . 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al (, Physical Review B)
    Diluted magnetic semiconductor (DMS) systems have been extensively studied in recent decades. DMSs provides a platform where charge transport and magnetic ordering phenomena exhibit unique interplays, together with possible applications to spin-dependent electronics (spintronics) devices. Initial development of ferromagnetic (FM) DMS systems centered around III-V semiconductors doped with dilute transition metals, such as (Ga,Mn)As, obtained by co-doping of spin and charge. More recently, independent spin and charge doping was first achieved in Li(Zn,Mn)As, a DMS system based on I-II-V semiconductor, with charge doping via variable Li concentrations and spin doping via iso-valent (Zn,Mn) substitutions. Although more than 30 new DMS systems with independent spin and charge doping have been synthesized since then, the main research emphasis has been put on development and characterization of systems with higher FM Curie temperature (TC) and different crystal structures suitable for possible formation of heterostructure devices. This article focuses on a new DMS material Na(Zn,Mn)Sb, which exhibits a spin glass (SG) ordering, together with metal-insulator transition (MIT) and colossal negative magnetoresistance (CMR) as a function of independent spin and charge doping and application of external magnetic fields. MIT and CMR phenomena are elucidated by magneto transport, magnetization, angle resolved photoemission spectroscopy (ARPES), and scanning tunneling microscopy (STM) measurements, and by band calculations which demonstrate development and disappearance of energy gap. Magnetic order and dynamic spin fluctuations are probed with muon spin relaxation (μSR) and magnetization, and the results for Na(Zn,Mn)Sb are compared to those from FM DMS systems Li(Zn,Mn)As, Li(Zn,Mn)P, and Li(Zn,Mn,Cu)As. First-principles calculations are performed for Na(Zn,Mn)Sb, (Ga,Mn)As and Li(Zn,Mn)P to highlight the roles of charge and spin doping on exchange interactions mediated by nearest neighbor super-exchange coupling and oscillatory Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling via conduction electrons. These studies reveal (1) MIT and CMR of Na(Zn,Mn)Sb manifest as a response to spin configurations as spin-driven transport phenomena; (2) a dynamic critical behavior is observed in SG transition of Na(Zn,Mn)Sb, in contrast to more first-order-like magnetic evolutions in other FM DMS systems; (3) charge doping supports FM coupling additive to direct AFM exchange interaction between nearest-neighbor Mn pairs; and (4) a widely different coercive fields seen in different families of FM and SG DMS systems can be explained by geometrical frustration of AFM interaction in underlying lattice for Mn spin network 
    more » « less
  3. ; ; ; ; ; ; (, Nanoscale)
    Realization of ferromagnetic (FM) interlayer coupling in magnetic topological insulators (TIs) of the MnBi 2 Te 4 family of materials (MBTs) may pave the way for realizing the high-temperature quantum anomalous Hall effect (high- T QAHE). Here we propose a generic dual d-band (DDB) model to elucidate the energy difference (Δ E = E AFM − E FM ) between the AFM and FM coupling in transition-metal (TM)-doped MBTs, where the valence of TMs splits into d-t 2g and d-e g sub-bands. Remarkably, the DDB shows that Δ E is universally determined by the relative position of the dopant (X) and Mn d-e g / t 2g bands, . If Δ E d > 0, then Δ E > 0 and the desired FM coupling is favored. This surprisingly simple rule is confirmed by first-principles calculations of hole-type 3d and 4d TM dopants. Significantly, by applying the DDB model, we predict the high- T QAHE in the V-doped Mn 2 Bi 2 Te 5 , where the Curie temperature is enhanced by doubling of the MnTe layer, while the topological order mitigated by doping can be restored by strain. 
    more » « less
  4. ; ; ; (, Journal of Materials Chemistry C)
    An analytical model using three-directional anisotropic (TDA) dispersion and a novel anisotropic relaxation time (RT) relation for modeling the thermal conductivity ( k ) of intercalated layered materials is developed. The TDA dispersion eliminates the restriction of in-plane isotropy and is suitable for TDA materials such as black phosphorous. We compare calculations of k of bulk intercalated layered materials using the isotropic Debye dispersion and BvK dispersion with our TDA dispersion model, paired with both isotropic and anisotropic RTs. We find that calculated k values by the TDA dispersion model agree best with the experimental data. Furthermore, anisotropic RTs largely improve the performance of the Debye and BvK dispersion models whose average relative deviations for the in-plane k are reduced from 17.3% and 23.0% to 4.4% and 8.5%, respectively. Finally, thermal conductivity accumulation functions of intercalated MoS 2 and graphite are numerically calculated based on the TDA dispersion with anisotropic RTs. These models predict that intercalants cause increased contributions from phonons with shorter mean free paths, especially for in-plane thermal conductivity. 
    more » « less
  5. ; ; ; ; ; ; (, Journal of Materials Chemistry A)
    The significant role of perovskite defect chemistry through A-site doping of strontium titanate with lanthanum for CO 2 electrolysis properties is demonstrated. Here we present a dual strategy of A-site deficiency and promoting adsorption/activation by making use of redox active dopants such as Mn/Cr linked to oxygen vacancies to facilitate CO 2 reduction at perovskite titanate cathode surfaces. Solid oxide electrolysers based on oxygen-excess La 0.2 Sr 0.8 Ti 0.9 Mn(Cr) 0.1 O 3+δ , A-site deficient (La 0.2 Sr 0.8 ) 0.9 Ti 0.9 Mn(Cr) 0.1 O 3−δ and undoped La 0.2 Sr 0.8 Ti 1.0 O 3+δ cathodes are evaluated. In situ infrared spectroscopy reveals that the adsorbed and activated CO 2 adopts an intermediate chemical state between a carbon dioxide molecule and a carbonate ion. The double strategy leads to optimal performance being observed after 100 h of high-temperature operation and 3 redox cycles, suggesting a promising cathode material for CO 2 electrolysis. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Text Encoded Conversion
  • XML
  • Save / Share this Record
  • Send to Email