| 1. |
- Flatten, Tim, et al.
(författare)
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Direct measurement of anisotropic conductivity in a nanolaminated (Mn0.5Cr0.5)(2)GaC thin film
- 2019
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Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 115:9
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Tidskriftsartikel (refereegranskat)abstract
- The direct and parameter-free measurement of anisotropic electrical resistivity of a magnetic M(n+1)AX(n) (MAX) phase film is presented. A multitip scanning tunneling microscope is used to carry out 4-probe transport measurements with variable probe spacing s. The observation of the crossover from the 3D regime for small s to the 2D regime for large s enables the determination of both in-plane and perpendicular-to-plane resistivities rho(ab) and rho(c). A (Cr0.5Mn0.5)(2)GaC MAX phase film shows a large anisotropy ratio rho(c)/rho(ab) = 525 +/- 49. This is a consequence of the complex bonding scheme of MAX phases with covalent M-X and metallic M-M bonds in the MX planes and predominately covalent, but weaker bonds between the MX and A planes. Published under license by AIP Publishing.
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| 2. |
- Lai, Chung-Chuan, et al.
(författare)
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Magnetic properties and structural characterization of layered (Cr0.5Mn0.5)(2)AuC synthesized by thermally induced substitutional reaction in (Cr0.5Mn0.5)(2)GaC
- 2018
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Ingår i: APL Materials. - : AMER INST PHYSICS. - 2166-532X. ; 6:2
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of the new phase (Cr0.5Mn0.5)(2)AuC are compared to the known MAX-phase (Cr0.5Mn0.5)(2)GaC, where the former was synthesized by thermally induced substitution reaction of Au for Ga in (Cr0.5Mn0.5)(2)GaC. The reaction introduced a lattice expansion of similar to 3% along the c-axis, an enhancement of the coercive field from 30 mT to 140 mT, and a reduction of the Curie temperature and the saturation magnetization. Still, (Cr0.5Mn0.5)(2)AuC displays similar features in the magnetic field-and temperature-dependent magnetization curves as previously reported magnetic MAX phases, e.g., (Cr0.5Mn0.5)(2)GaC and (Mo0.5Mn0.5)(2)GaC. Thework suggests a pathway for tuning the magnetic properties of MAX phases. (c) 2018 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license.
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| 3. |
- Lyaschenko, Sergey, et al.
(författare)
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Optical and magneto-optical properties of epitaxial Mn2GaC MAX phase thin film
- 2021
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Ingår i: Journal of Magnetism and Magnetic Materials. - : ELSEVIER. - 0304-8853 .- 1873-4766. ; 528
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Tidskriftsartikel (refereegranskat)abstract
- We report measurements of the dielectric permittivity, optical conductivity and magnetic circular dichroism (MCD) of the epitaxial Mn2GaC MAX-phase thin film in an external magnetic field of up to 200 mT, at temperatures of 296 and 140 K and 1.4 to 3.5 eV. The optical conductivity and MCD spectra show absorption peaks which are consistent with the interband electronic transitions for different positions of Mn, Ga, and C ions as confirmed by theoretical calculations of the spin-dependent density of electronic states. The well-known structural phase transition at 214 K is also seen in the changes of optical, magneto-optical and surface magnetic properties of Mn2GaC in our experiment.
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| 4. |
- Novoselova, Iuliia P., et al.
(författare)
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Large uniaxial magnetostriction with sign inversion at the first order phase transition in the nanolaminated Mn2GaC MAX phase
- 2018
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Ingår i: Scientific Reports. - London : NATURE PUBLISHING GROUP. - 2045-2322. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- In 2013, a new class of inherently nanolaminated magnetic materials, the so called magnetic MAX phases, was discovered. Following predictive material stability calculations, the hexagonal Mn2GaC compound was synthesized as hetero-epitaxial films containing Mn as the exclusive M-element. Recent theoretical and experimental studies suggested a high magnetic ordering temperature and non-collinear antiferromagnetic (AFM) spin states as a result of competitive ferromagnetic and antiferromagnetic exchange interactions. In order to assess the potential for practical applications of Mn2GaC, we have studied the temperature-dependent magnetization, and the magnetoresistive, magnetostrictive as well as magnetocaloric properties of the compound. The material exhibits two magnetic phase transitions. The Neel temperature is T-N similar to 507 K, at which the system changes from a collinear AFM state to the paramagnetic state. At T-t = 214 K the material undergoes a first order magnetic phase transition from AFM at higher temperature to a non-collinear AFM spin structure. Both states show large uniaxial c-axis magnetostriction of 450 ppm. Remarkably, the magnetostriction changes sign, being compressive (negative) above T-t and tensile (positive) below the T-t. The sign change of the magnetostriction is accompanied by a sign change in the magnetoresistance indicating a coupling among the spin, lattice and electrical transport properties.
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| 5. |
- Novoselova, Iuliia P., et al.
(författare)
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Long-term stability and thickness dependence of magnetism in thin (Cr0.5Mn0.5)(2)GaC MAX phase films
- 2019
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Ingår i: Materials Research Letters. - : TAYLOR & FRANCIS INC. - 2166-3831. ; 7:4, s. 159-163
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Tidskriftsartikel (refereegranskat)abstract
- The thickness dependence and long-term stability of the magnetic properties of epitaxial (Cr0.5Mn0.5)(2)GaC MAX phase films on MgO (111) were investigated. For 12.5- to 156-nm-thick films, which corresponds to 10-125 c-axis unit cells, samples were found to be phase pure with negligible c-axis lattice strain of less than 10(-4) nm even for the thinnest films. No influence of the interface layers on the magnetic anisotropy, the magnetization or the para- to ferromagnetic phase transition was observed. All samples remained stable for more than one year in ambient conditions. [GRAPHICS] IMPACT STATEMENT The complex temperature- and magnetic field-dependent magnetism of electrically conducting (Cr0.5Mn0.5)(2)GaC MAX phase films is environmentally robust over one year and independent on interface effects.
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| 6. |
- Pazniak, Hanna, et al.
(författare)
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Phase Stability of Nanolaminated Epitaxial (Cr1-xFex)(2)AlC MAX Phase Thin Films on MgO(111) and Al2O3 (0001) for Use as Conductive Coatings
- 2021
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Ingår i: ACS Applied Nano Materials. - : AMER CHEMICAL SOC. - 2574-0970. ; 4:12, s. 13761-13770
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we model the chemical stability in the (Cr1-xFex)(2)AlC MAX phase system using density functional theory, predicting its phase stability for 0 < x < 0.2. Following the calculations, we have successfully synthesized nanolaminated (Cr1-xFex)(2)AlC MAX phase thin films with target Fe contents of x = 0.1 and x = 0.2 by pulsed laser deposition using elemental targets on MgO(111) and Al2O3 (0001) substrates at 600 degrees C. Structural investigations by X-ray diffraction and transmission electron microscopy reveal MAX phase epitaxial Iilms on both substrates with a coexisting (Fe,Cr)(5)Al-8 intermetallic secondary phase. Experiments suggest an actual maximum Fe solubility of 3.4 at %, corresponding to (Cr0.932Fe0.068)(2)AlC, which is the highest Fe doping level achieved so far in volume materials and thin films. Residual Fe is continuously distributed in the (Fe,Cr)(5)Al-8 intermetallic secondary phase. The incorporation of Fe results in the slight reduction of the c lattice parameter, while the a lattice parameter remains unchanged. The nanolaminated (Cr0.932Fe0.068)(2)AlC thin films show a metallic behavior and can serve as promising candidates for highly conductive coatings.
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| 7. |
- Salikhov, Ruslan, et al.
(författare)
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Magnetic Anisotropy in the (Cr0.5Mn0.5)(2)GaC MAX Phase
- 2015
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Ingår i: Materials Research Letters. - : TAYLOR & FRANCIS INC. - 2166-3831. ; 3:3, s. 156-160
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic MAX phase (Cr0.5Mn0.5)(2)GaC thin films grown epitaxially on MgO(111) substrates were studied by ferromagnetic resonance at temperatures between 110 and 300 K. The spectroscopic splitting factor g = 2.00 +/- 0.01 measured at all temperatures indicates pure spin magnetism in the sample. At all temperatures we find the magnetocrystalline anisotropy energy to be negligible which is in agreement with the identified pure spin magnetism.
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| 8. |
- Tao, Quanzheng, et al.
(författare)
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Atomically Layered and Ordered Rare-Earth i-MAX Phases : A New Class of Magnetic Quaternary Compounds
- 2019
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 31:7, s. 2476-2485
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Tidskriftsartikel (refereegranskat)abstract
- In 2017, we discovered quaternary i-MAX phases atomically layered solids, where M is an early transition metal, A is an A group element, and X is C—with a (M12/3M21/3)2AC chemistry, where the M1 and M2 atoms are in-plane ordered. Herein, we report the discovery of a class of magnetic i-MAX phases in which bilayers of a quasi-2D magnetic frustrated triangular lattice overlay a Mo honeycomb arrangement and an Al Kagome lattice. The chemistry of this family is (Mo2/3RE1/3)2AlC, and the rare-earth, RE, elements are Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. The magnetic properties were characterized and found to display a plethora of ground states, resulting from an interplay of competing magnetic interactions in the presence of magnetocrystalline anisotropy.
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| 9. |
- Tao, Quanzheng, et al.
(författare)
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Magnetic phase diagram of (Mo2/3RE1/3)(2)AlC, RE = Tb and Dy, studied by magnetization, specific heat, and neutron diffraction analysis
- 2022
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Ingår i: Journal of Physics. - : IOP Publishing Ltd. - 0953-8984 .- 1361-648X. ; 34:21
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Tidskriftsartikel (refereegranskat)abstract
- We report the results of magnetization, heat capacity, and neutron diffraction measurements on (Mo2/3RE1/3)(2)AlC with RE = Dy and Tb. Temperature and field-dependent magnetization as well as heat capacity were measured on a powder sample and on a single crystal allowing the construction of the magnetic field-temperature phase diagram. To study the magnetic structure of each magnetic phase, we applied neutron diffraction in a magnetic field up to 6 T. For (Mo2/3Dy1/3)(2)AlC in zero field, a spin density wave is stabilized at 16 K, with antiferromagnetic ordering at 13 K. Furthermore, we identify the coexistence of ferromagnetic and antiferromagnetic phases induced by magnetic fields for both RE = Tb and Dy. The origin of the field induced phases is resulting from the competing ferromagnetic and antiferromagnetic interactions.
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| 10. |
- Tao, Quanzheng, et al.
(författare)
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Synthesis, Characterization, and Modeling of a Chemically Ordered Quaternary Boride, Mo4MnSiB2
- 2023
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Ingår i: Crystal Growth & Design. - : AMER CHEMICAL SOC. - 1528-7483 .- 1528-7505. ; 23:5, s. 3258-3263
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Tidskriftsartikel (refereegranskat)abstract
- The recent discovery of chemical ordering in quaternary borides offers new ways of exploring properties and functionalities of these laminated phases. Here, we have synthesized and investigated chemical ordering of the laminated Mo4MnSiB2 (T2) phase, thereby introducing a magnetic element into the family of materials coined o-MAB phases. By X-ray diffraction and scanning transmission electron microscopy, we provide evidence for out-of-plane chemical ordering of Mo and Mn, with Mo occupying the 16l site and Mn preferentially residing in the 4c site. Mn and B constitute quasi-two-dimensional layers in the laminated material. We have therefore also studied the magnetic properties by magnetometry, and no sign of long-range magnetic order is observed. An initial assessment of the magnetic ordering has been further studied by density functional theory (DFT) calculations, and while we find an antiferromagnetic configuration to be the most stable one, ferromagnetic ordering is very close in energy.
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