مجال
التميز
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تميز دراسي وبحثي وإبداع علمي
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البحوث المنشورة
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البحث (1):
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عنوان البحث:
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New
Bandgap Measurement Technique for a Half-Metallic Ferromagnet
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رابط إلى البحث:
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Click
here
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تاريخ النشر:
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18 Nov 2014
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موجز عن البحث:
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In this paper, we report our new optical
method for the measurement of the bandgaps of half-metallic ferromagnets
(HMFs). We measured the bandgap of polycrystalline Co2FeSi Heusler alloy thin
films at room temperature (RT). The Co2FeSi thin films were deposited on
MgO(001) and Si/SiO2 substrates by sputter deposition. Circularly polarized
infrared light was used to excite the corresponding spin-polarized electrons,
which were effectively absorbed by the bandgap of the Co2FeSi Heusler alloy.
The Co2FeSi bandgap energy was repeatedly measured and it was found to be
~0.094 eV at RT. This technique allows us to characterize the spin bandgap of
HMFs directly.
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البحث (2):
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عنوان البحث:
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Direct band-gap
measurement on epitaxial Co2FeAl0.5Si0.5 Heusler-alloy films
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رابط إلى البحث:
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here
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تاريخ النشر:
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03 April
2015
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موجز عن البحث:
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In this study, a
newly developed band-gap measurement technique has been used to characterize
epitaxial Co2FeAl0.5Si0.5 (CFAS) films. The CFAS films were deposited on
MgO(001) substrate by ultra-high vacuum molecular beam epitaxy. The band-gap
for the as deposited films was found to be ~110 meV when measured at room
temperature. This simple technique provides a macroscopic analysis of the
half-metallic properties of a thin film. This allows for simple optimisation
of growth and annealing conditions.
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المؤتمرات العلمية:
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المؤتمر (1):
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عنوان المؤتمر:
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JSPS
York-Tohoku Research Symposium
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تاريخ الإنعقاد:
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27-29/06/2011
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مكان
الإنعقاد:
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York,
UK
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طبيعة المشاركة:
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Poster
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عنوان المشاركة:
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Development
and Characterisation of a New Ferromagnetic Ultrathin Films
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ملخص المشاركة:
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Spintronics devices have three key
requirements; high spin polarisation, high Curie temperature (Tc)
above room temperature (RT), and the conductance match at an interface.
Half-metallic ferromagnets (HMFs) can fulfil these requirements due to their
ability to exhibit 100% spin polarisation at the Fermi level (EF).
There are four categories of materials that are theoretically predicted to be
HMFs; Heusler alloys, zinc-blend compounds, oxide compounds, and perovskites.
The aim of this study is to develop a new technique to directly measure the
spin density of states of the Heusler alloys. This technique will allow
characterisation of the band structures in Heusler as well as other HMFs.
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المؤتمر (2):
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عنوان المؤتمر:
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Current
Research in Magnetism Workshop (CRIM 2011)
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تاريخ الإنعقاد:
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21/09/2011
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مكان
الإنعقاد:
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Durham,
UK
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طبيعة المشاركة:
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Poster
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عنوان المشاركة:
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Development
of a New Characterisation Technique for Half-Metallic Ferromagnetic Ultrathin
Films
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ملخص المشاركة:
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In this study, Co-based full-Heusler alloys
are used due to good lattice constant matching with major III-V
semiconductors, high Curie temperature (greater than 950K for Co2MnSi),
and the ability to control spin density of states (DOS) at the EF. The aim of this study is to develop a new
technique to directly measure the spin density of states of the Heusler
alloys. Circularly polarised infrared (IR) light will be used to excite only
the minority spins in the Heusler alloys. This technique will allow
characterisation of the band structures in Heusler as well as other HMFs.
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المؤتمر (3):
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عنوان المؤتمر:
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INTERMAG 2014 – IEEE International
Magnetics Conference
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تاريخ الإنعقاد:
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04-08
May 2014
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مكان
الإنعقاد:
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Dresden, Germany
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طبيعة المشاركة:
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Oral
presentation
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عنوان المشاركة:
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New Bandgap Measurement Technique for a
Half-Metallic Ferromagnet
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ملخص المشاركة:
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In this paper, we report our new
optical method for the measurement of the bandgaps of half-metallic
ferromagnets (HMFs). We measured the bandgap of polycrystalline Co2FeSi
Heusler alloy thin films at room temperature (RT). The Co2FeSi thin films
were deposited on MgO(001) and Si/SiO2 substrates by sputter deposition.
Circularly polarized infrared light was used to excite the corresponding
spin-polarized electrons, which were effectively absorbed by the bandgap of
the Co2FeSi Heusler alloy. The Co2FeSi bandgap energy was repeatedly measured
and it was found to be ~0.094 eV at RT. This technique allows us to
characterize the spin bandgap of HMFs directly.
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المؤتمر (4):
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عنوان المؤتمر:
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The 7th Saudi International
Conference 2014
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تاريخ الإنعقاد:
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01-02/02/2014
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مكان
الإنعقاد:
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Edinburgh, UK
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طبيعة المشاركة:
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Poster
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عنوان المشاركة:
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New band-gap measurement technique for
a half-metallic ferromagnet
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ملخص المشاركة:
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The HMFs are new class of materials
that have unique band structures; the majority spin channel has a metallic
band structure whereas the minority spin channel has a semiconducting band
structure with a band gap at EF. In this study, Co-based
full-Heusler alloys were used due to good lattice matching with major
heterostructures and Tc > RT. The main aim of this study is to
develop a new technique to directly measure the band-gap of the HMFs. This
technique allowed us to characterise the width and distribution of the
minority spin band-gap.
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المؤتمر (5):
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عنوان المؤتمر:
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Magnetism 2014
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تاريخ الإنعقاد:
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07-08/04/2014
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مكان
الإنعقاد:
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Manchester, UK
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طبيعة المشاركة:
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Poster
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عنوان المشاركة:
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New band-gap
measurement technique for a half-metallic ferromagnet
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ملخص المشاركة:
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In this
study, we report our new method to measure the HMF band-gap optically, which
is sensitive to both surface/interface and bulk regions of the HMF by
controlling the light penetration. We demonstrate the potential of our method
by measuring the band-gap of Co2FeSi Heusler- alloy films, which
are theoretically predicted to be a HMF at RT. This technique allows us to
characterise the spin band-gap of half-metallic ferromagnets reproducibly.
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المؤتمر (6):
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عنوان المؤتمر:
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Magnetism 2015
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تاريخ الإنعقاد:
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30-31/03/2015
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مكان
الإنعقاد:
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Leeds, UK
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طبيعة المشاركة:
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Poster
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عنوان المشاركة:
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Direct band-gap measurement on a NiMnSb
Heusler alloy at room temperature
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ملخص المشاركة:
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We recently developed a new technique
to measurement a band-gap (Eg)
in a half-metallic ferromagnet using circularly polarised photoexcitation. We
reported Eg of the minority spin band in full-Heusler
alloys and have extended our study to a half-Heusler alloy of NiMnSb. Eg
of bulk NiMnSb half-Heusler alloy was
measured at room temperature (RT) using our recently developed technique. Eg for NiMnSb has
been calculated to be 500 meV at 0 K, shrinking
at higher temperatures as the overall magnetisation drops. These measurements confirm the ability
of our technique to measure Eg of a wide range of Heusler alloys at RT.
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جوائز التكريم:
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الجائزة (1):
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مسمى الجائزة:
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3rd
Prize (in the 2nd year PhD student poster competition)
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الجهة المانحة:
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Electronics
Department, University of York
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تاريخ الجائزة:
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20/02/2012
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مجال التكريم:
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Development
of a Band-gap Measurement Technique for Half-Metallic Ferromagnetic Ultrathin
Films
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