1. Department of PhysicsBahauddin Zakariya University Multan 60800 Pakistan
2. Nanoscience & Technology DepartmentNational Centre for Physics Shahdra Valley Road Quaid-i-Azam University Campus Islamabad 45320 Pakistan
3. Department of PhysicsFaculty of SciencesUniversity of Gujrat Hafiz Hayat Campus Gujrat 50700 Pakistan
4. School of MaterialsThe University of Manchester Oxford Road Manchester M13 9PL U.K.