Magnetic Ordering in Fe 0.008 Ge 1 jx D x (D = As, Bi) NARENDRA PATEL 1, * , MUKESH CHAWDA 1 , MITESH SARKAR 1 , K. C. SEBASTIAN 1 , D. R. S. SOMAYAJULU 1 and AJAY GUPTA 2 1 Department of Physics, M. S. University of Baroda, Baroda, India; e-mail: narendra_msu@yahoo.co.in 2 Inter University Consortium, Indore, India Abstract. The formation of local moments and the effect of charge carriers in dilute magnetic semiconductors can be well understood using local probe techniques like Mossbauer Spectroscopy. We report here on Mossbauer studies in the systems Fe 0.008 Ge 1jx D x (D = As, Bi), Fe 0.008 Ge 1jx In x , and Fe 0.008 Ge 1 j x Sn x . At room temperature magnetic interactions were observed for donor (D) impurities at the Fe site in the Fe 0.008 Ge system. No such magnetic ordering was observed for acceptor (In) or neutral (Sn) impurities. Key Words: dilute magnetic semiconductors, magnetic ordering, Mossbauer spectroscopy. 1. Introduction The theory of carrier-induced ferromagnetism in Dilute Magnetic Semi- conductors (DMS) [1, 2] has effectively explained the mechanism to raise the Curie temperature to room temperature and above. The above-room-temperature ferro-magnetism in Mn-doped IIIYV-group semiconductors ZnO [3], GaN [4] and GaP [5] is well understood through this mechanism, where a long-range interaction between Mn 2+ ions occurs via mediated polarised itinerant carriers. Such carrier-induced magnetic ordering was also observed in other IVYVI compound systems such as GeTe doped with Cr, Mn or Fe [6], but the Curie temperatures were much below room temperature. The itinerant carriers (especially holes) responsible for the magnetic interactions in all these materials are brought by controlled doping of acceptor impurities of transition metals like Mn or Fe in nonmagnetic lattice sites of the compound semiconductors. Thus hole-mediated ferromagnetism is now well known, but the electron-mediated ferromagnetism (i.e., in the n-type material) is yet to be achieved at room temperature. Here we investigate the effect of dilute donor impurities (As, Bi) in Fe 0.008 Ge alloys. In such dilute systems the local probe hyperfine interaction studies are * Author for correspondence. Hyperfine Interactions (2005) 160:247–252 DOI 10.1007/s10751-005-9158-4 # Springer 2005