TY - JOUR
T1 - Ordering tendencies and electronic properties in quaternary Heusler derivatives
AU - Neibecker, Pascal
AU - Gruner, Markus E.
AU - Xu, Xiao
AU - Kainuma, Ryosuke
AU - Petry, Winfried
AU - Pentcheva, Rossitza
AU - Leitner, Michael
N1 - Funding Information:
This work was funded by the Deutsche Forschungsgemeinschaft (DFG) within the Transregional Collaborative Research Center TRR 80 From electronic correlations to functionality. P.N. acknowledges additional support from the Japan Society for the Promotion of Science (JSPS) via a short-term doctoral scholarship for research in Japan. We thank O. Dolotko and A. Senyshyn of the MLZ for facilitating the neutron diffraction measurements. SQUID measurements were performed at the Center for Low Temperature Science, Institute for Materials Research, Tohoku University. Computing resources for the supercell calculations were kindly provided by the Center for Computational Sciences and Simulation (CCSS) at University of Duisburg-Essen on the supercomputer magnitUDE (DFG Grants No. INST 20876/209-1 FUGG and No. INST 20876/243-1 FUGG).
Funding Information:
This work was funded by the Deutsche Forschungsgemeinschaft (DFG) within the Transregional Collaborative Research Center TRR 80 “From electronic correlations to functionality.” P.N. acknowledges additional support from the Japan Society for the Promotion of Science (JSPS) via a short-term doctoral scholarship for research in Japan. We thank O. Dolotko and A. Senyshyn of the MLZ for facilitating the neutron diffraction measurements. SQUID measurements were performed at the Center for Low Temperature Science, Institute for Materials Research, Tohoku University. Computing resources for the supercell calculations were kindly provided by the Center for Computational Sciences and Simulation (CCSS) at University of Duisburg-Essen on the supercomputer magnitUDE (DFG Grants No. INST 20876/209-1 FUGG and No. INST 20876/243-1 FUGG).
Publisher Copyright:
© 2017 authors. Published by the American Physical Society.
PY - 2017/10/16
Y1 - 2017/10/16
N2 - The phase stabilities and ordering tendencies in the quaternary full-Heusler alloys NiCoMnAl and NiCoMnGa have been investigated by in situ neutron diffraction, calorimetry, and magnetization measurements. NiCoMnGa was found to adopt the L21 structure, with distinct Mn and Ga sublattices but a common Ni-Co sublattice. A second-order phase transition to the B2 phase with disorder also between Mn and Ga was observed at 1160K. In contrast, in NiCoMnAl slow cooling or low-temperature annealing treatments are required to induce incipient L21 ordering, otherwise the system displays only B2 order. Linked to L21 ordering, a drastic increase in the magnetic transition temperature was observed in NiCoMnAl, while annealing affected the magnetic behavior of NiCoMnGa only weakly due to the low degree of quenched-in disorder. First principles calculations were employed to study the thermodynamics as well as order-dependent electronic properties of both compounds. It was found that a near half-metallic pseudogap emerges in the minority spin channel only for the completely ordered Y structure. However, this structure is energetically unstable compared to a tetragonal structure with alternating layers of Ni and Co, which is predicted to be the low-temperature ground state. The experimental inaccessibility of the totally ordered structures is explained by kinetic limitations due to the low ordering energies.
AB - The phase stabilities and ordering tendencies in the quaternary full-Heusler alloys NiCoMnAl and NiCoMnGa have been investigated by in situ neutron diffraction, calorimetry, and magnetization measurements. NiCoMnGa was found to adopt the L21 structure, with distinct Mn and Ga sublattices but a common Ni-Co sublattice. A second-order phase transition to the B2 phase with disorder also between Mn and Ga was observed at 1160K. In contrast, in NiCoMnAl slow cooling or low-temperature annealing treatments are required to induce incipient L21 ordering, otherwise the system displays only B2 order. Linked to L21 ordering, a drastic increase in the magnetic transition temperature was observed in NiCoMnAl, while annealing affected the magnetic behavior of NiCoMnGa only weakly due to the low degree of quenched-in disorder. First principles calculations were employed to study the thermodynamics as well as order-dependent electronic properties of both compounds. It was found that a near half-metallic pseudogap emerges in the minority spin channel only for the completely ordered Y structure. However, this structure is energetically unstable compared to a tetragonal structure with alternating layers of Ni and Co, which is predicted to be the low-temperature ground state. The experimental inaccessibility of the totally ordered structures is explained by kinetic limitations due to the low ordering energies.
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U2 - 10.1103/PhysRevB.96.165131
DO - 10.1103/PhysRevB.96.165131
M3 - Article
AN - SCOPUS:85038110049
VL - 96
JO - Physical Review B
JF - Physical Review B
SN - 2469-9950
IS - 16
M1 - 165131
ER -