RESEARCH

I have investigated the generation of spin triplet superconductivity at the interface of a conventional superconductor and a half metallic ferromagnet CrO₂, which leads to a long-ranged proximity effect. Conventional spin-singlet Cooper pairs dephase in a ferromagnet under the effect of its exchange field over a coherence length, which cannot be more that few nm. However, such a dephasing does not occur with spin triplet Cooper pair. The triplet correlations can be induced at a superconductor / ferromagnet (S/F) interface via some sort of magnetic inhomogeneity, for instance domain walls or unaligned magnetic moments.

CrO₂-based S/F/S devices were fabricated using a-MoGe superconductor in lateral geometry with a spacing of 700 nm (Fig. a). Long ranged supercurrents are observed when the devises are fabricated on sapphire substrates. But in case of TiO₂ substrates, we do not find supercurrents. CrO₂ can be grown only via Chemical Vapor Deposition on few selected substrates like sapphire or TiO₂. On sapphire it grows in the form of rectangular grains aligned at 60o degree to each other. The resulting magnetic anisotropy is providing a required inhomogeneity to generate long-ranged supercurrents. While on TiO₂ the grains have two-fold rotational symmetry and uniaxial anisotropy, which cannot provide required magnetic inhomogeneity. To solve this problem, we create artificial magnetic inhomogeneity by sputtering another ferromagnetic thin layer of Ni over CrO₂. In this way we observed rather strong proximity effect over the length of 800 nm (Fig. b).

 

In this topological quantum phenomena project, I am planning to investigate the Josephson effects based Sr₂RuO₄, which is most probably a chiral p-wave spin triplet superconductor. We prepare conventional-superconductor/Ru/Sr₂RuO₄ junctions to investigate the interference between a conventional s-wave spin singlet superconductor and a chiral p-wave spin triplet superconductor. It has been realized that such a superconducting interference exhibits topological nature. The chiral p-wave superconductivity of Sr₂RuO₄ may even generate a half quantum vortex. It has been found that Sr₂RuO₄ exhibits a half fluxoid jumps from magnetic torque measurements. We will also fabricate micrometer-sized rings of Sr₂RuO₄to confirm the half fluxoid generation using transport phenomena.

EDUCATION

2001

BSc, Punjab University-Pakistan

2006

MSc+M.Phil, University of Engineering and Technology Lahore-Pakistan

2011

Ph.D., Leiden University (Advisor: Prof. Dr. Jan Aarts)

PROFESSIONAL EXPERIENCE

2004-2007

Lecturer, University of Engineering and Technology Lahore-Pakistan

PUBLICATIONS RELATED TO THIS PROJECT

SELECTION OF PUBLICATIONS

"Long range supercurrents in ferromagnetic CrO2 using a multilayer contact structure",
M. S. Anwar, M. Veldhorst, A. Brinkman, and J. Aarts
Appl. Phys. Lett. 100, 052602 (2012).

"Inducing supercurrents in thin films of ferromagnetic CrO₂",
M. S. Anwar, and J. Aarts,
Supercond. Sci. Technol. 24, 024016 (2011).

"Long range supercurrents through half-metallic ferromagnetic CrO₂",
M. S. Anwar, F. Czeschka, M. Hesselberth, M. Porcu, J. Aarts,
Phys. Rev. B. 82, 100501(R) (2010).

"Influence of number of laser shots on laser induced microstructures on Ag and Cu target",
A Latif, M. S. Anwar,M. A. Aleem, M. S. Rafique, M. Khaleeq-ur-Rahman,
Laser Part. Beams. 27,129 (2009).

"Laser Induced Exfoliation Splashing in Glass Materials",
M. Khaleeq-ur-Rahman, M. S. Anwar,M. S. Rafique, and K. W. Haider,
Nucl. Inst. and Meth.B 255, 338 (2007).

"Theoretical model for heat conduction in metals during interaction with ultra short laser pulse",
M. S. Anwar, A. Latif, M. Iqbal, M. S. Rafique, M. Khaleeq-ur-Rahman and S. Siddique,
Laser Part. Beams 24, 347 (2006).

"Angular distribution and forward peaking in laser produced plasma ions",
M. S. Rafique, M. Khaleeq-ur-Rahman, M. S. Anwar, F. Mahmood, A. Ashfaq and K. Siraj,
Laser Part. Beams 32, 131 (2005).