TY - JOUR
T1 - Magnetic tunnel junctions with a B2-ordered CoFeCrAl equiatomic Heusler alloy
AU - Tsuchiya, Tomoki
AU - Roy, Tufan
AU - Elphick, Kelvin
AU - Okabayashi, Jun
AU - Bainsla, Lakhan
AU - Ichinose, Tomohiro
AU - Suzuki, Kazuya Z.
AU - Tsujikawa, Masahito
AU - Shirai, Masafumi
AU - Hirohata, Atsufumi
AU - Mizukami, Shigemi
N1 - Funding Information:
T.T. and S.M. thank Y. Kondo for his technical support. This work was partially supported by JST CREST (Grant No. JPMJCR17J5), JSPS Core-to-Core Program, and KAKENHI (Grant No. 17F17063).
Funding Information:
This work was partially supported by JST CREST (Grant No. JPMJCR17J5), JSPS Core-to-Core Program, and KAKENHI (Grant No. 17F17063).
Publisher Copyright:
© 2019 American Physical Society.
PY - 2019/8/5
Y1 - 2019/8/5
N2 - The equiatomic quaternary Heusler alloy CoFeCrAl is a candidate material for spin-gapless semiconductors (SGSs). However, to date, there have been no experimental attempts at fabricating a junction device. This paper reports a fully epitaxial (001)-oriented MgO barrier magnetic tunnel junction (MTJ) with CoFeCrAl electrodes grown on a Cr buffer. X-ray and electron diffraction measurements show that the (001) CoFeCrAl electrode films with atomically flat surfaces have a B2-ordered phase. The saturation magnetization is 380emu/cm3, almost the same as the value given by the Slater-Pauling-like rule, and the maximum tunnel magnetoresistance ratios at 300 K and 10 K are 87% and 165%, respectively. Cross-sectional electron diffraction analysis shows that the MTJs have MgO interfaces with fewer dislocations. The temperature- A nd bias-voltage-dependence of the transport measurements indicates magnon-induced inelastic electron tunneling overlapping with the coherent electron tunneling. X-ray magnetic circular dichroism (XMCD) measurements show a ferromagnetic arrangement of the Co and Fe magnetic moments of B2-ordered CoFeCrAl, in contrast to the ferrimagnetic arrangement predicted for the Y-ordered state possessing SGS characteristics. Ab initio calculations taking account of the Cr-Fe swap disorder qualitatively explain the XMCD results. Finally, the effect of the Cr-Fe swap disorder on the ability for electronic states to allow coherent electron tunneling is discussed.
AB - The equiatomic quaternary Heusler alloy CoFeCrAl is a candidate material for spin-gapless semiconductors (SGSs). However, to date, there have been no experimental attempts at fabricating a junction device. This paper reports a fully epitaxial (001)-oriented MgO barrier magnetic tunnel junction (MTJ) with CoFeCrAl electrodes grown on a Cr buffer. X-ray and electron diffraction measurements show that the (001) CoFeCrAl electrode films with atomically flat surfaces have a B2-ordered phase. The saturation magnetization is 380emu/cm3, almost the same as the value given by the Slater-Pauling-like rule, and the maximum tunnel magnetoresistance ratios at 300 K and 10 K are 87% and 165%, respectively. Cross-sectional electron diffraction analysis shows that the MTJs have MgO interfaces with fewer dislocations. The temperature- A nd bias-voltage-dependence of the transport measurements indicates magnon-induced inelastic electron tunneling overlapping with the coherent electron tunneling. X-ray magnetic circular dichroism (XMCD) measurements show a ferromagnetic arrangement of the Co and Fe magnetic moments of B2-ordered CoFeCrAl, in contrast to the ferrimagnetic arrangement predicted for the Y-ordered state possessing SGS characteristics. Ab initio calculations taking account of the Cr-Fe swap disorder qualitatively explain the XMCD results. Finally, the effect of the Cr-Fe swap disorder on the ability for electronic states to allow coherent electron tunneling is discussed.
UR - http://www.scopus.com/inward/record.url?scp=85070543514&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85070543514&partnerID=8YFLogxK
U2 - 10.1103/PhysRevMaterials.3.084403
DO - 10.1103/PhysRevMaterials.3.084403
M3 - Article
AN - SCOPUS:85070543514
VL - 3
JO - Physical Review Materials
JF - Physical Review Materials
SN - 2475-9953
IS - 8
M1 - 084403
ER -