A Group-IV Ferromagnetic Semiconductor: Mn _x Ge _{1− x}

Abstract

We report on the epitaxial growth of a group-IV ferromagnetic semiconductor, Mn(x)Ge(1-x), in which the Curie temperature is found to increase linearly with manganese (Mn) concentration from 25 to 116 kelvin. The p-type semiconducting character and hole-mediated exchange permit control of ferromagnetic order through application of a +/-0.5-volt gate voltage, a value compatible with present microelectronic technology. Total-energy calculations within density-functional theory show that the magnetically ordered phase arises from a long-range ferromagnetic interaction that dominates a short-range antiferromagnetic interaction. Calculated spin interactions and percolation theory predict transition temperatures larger than measured, consistent with the observed suppression of magnetically active Mn atoms and hole concentration.

Tadpole shaped Ge0.96Mn0.04 magnetic semiconductors grown on Si

“…The GeMn tadpoles exhibit a saturation moment of 25 kA/m ͑at 10 K͒ compared with the reported value of ϳ8 kA/ m for Ge 0.98 Mn 0.02 . 2 The saturation moments per Mn atom can be estimated to be 0.9 B . Provided that each Mn has a theoretical moment of 3 B , [19][20][21] this gives a faction of roughly 30% of Mn being activated in the GeMn layer.…”

“…1 For this reason, Ge-based ͑such as GeMn͒ diluted magnetic semiconductors ͑DMSs͒, compatible with the current Si technology, have been studied extensively. [2][3][4][5][6][7][8][9][10][11][12][13] It is well understood that the low solubility of Mn in Ge has been a main barrier to achieve a high T c DMS GeMn film with high Mn concentration and uniformly distributed Mn in Ge. As a consequence, Mn-rich precipitates, such as Mn 5 Ge 3 , 9,14,15 Mn 5 Ge 2 , and Mn 11 Ge 8 , 12 are usually observed and are believed to be responsible for the observed ferromagnetism up to room temperature.…”

The composition, structure and optical properties of weakly magnetic Co-containing amorphous Si and Ge films

“…With the purpose of developing ferromagnetic semiconductors compatible with the current (micro-) electronics industry, group-IV semiconductors doped with Mn were also recently studied in detail [3][4][5]. However, the insertion of Mn in crystalline silicon (c-Si) and germanium (c-Ge) has been very limited [3,5].…”

How to make semiconductors ferromagnetic: a first course on spintronics

“…Following the successful development of Ga 1−x Mn x As 3,4,5 and In 1−x Mn x As 6 as ferromagnetic semiconductors (with x ≈ 1 − 10%) using careful low-temperature molecular beam epitaxy (MBE) technique, intensive worldwide activity has led to claims of ferromagnetism (some at room temperatures and above) in several magnetically doped semiconductors, e.g. GaMnP, 7 GaMnN, 8 GeMn, 9 GaMnSb. 10 It is at present unclear whether all these reports of ferromagnetism (particularly at room temperatures or above) are indeed intrinsic magnetic behavior or are arising from clustering and segregation effects associated with various Mn-complexes (which have low solubility) and related materials problems.…”