Search arXiv⌕ Search

arXiv · cond-mat/0503185

Ferromagnetic Semiconductors: Moving Beyond (Ga,Mn)As

Abstract

The recent development of MBE techniques for growth of III-V ferromagnetic semiconductors has created materials with exceptional promise in spintronics, i.e. electronics that exploit carrier spin polarization. Among the most carefully studied of these materials is (Ga,Mn)As, in which meticulous optimization of growth techniques has led to reproducible materials properties and ferromagnetic transition temperatures well above 150 K. We review progress in the understanding of this particular material and efforts to address ferromagnetic semiconductors as a class. We then discuss proposals for how these materials might find applications in spintronics. Finally, we propose criteria that can be used to judge the potential utility of newly discovered ferromagnetic semiconductors, and we suggest guidelines that may be helpful in shaping the search for the ideal material.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A. H. MacDonald, P. Schiffer, N. Samarth. 2005-03-08. Ferromagnetic Semiconductors: Moving Beyond (Ga,Mn)As. https://doi.org/10.1038/nmat1325

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

Symmetry-induced magnetic fullerene

Defect-free, charge-neutral, pure-carbon materials are generally viewed as intrinsically non-magnetic. Here we challenge this view by establishing a fundamental principle of symmetry-induced magnetism in pure-carbon fullerene systems through molecular orbital theory. We show that high-order symmetry of fullerene molecules or their crystalline lattices induces degenerate energy levels and hence, quantised magnetic moments at half filling. This mechanism holds for all high-order symmetries. It suggests a plausible intrinsic origin for the previously debated magnetic fullerene. Additionally, recent experimental advances in the synthesis of monolayer fullerene networks provide a feasible platform to implement our prediction on the deep link between symmetry and magnetism in these systems. Our results create new, broad frontiers of quantum magnetism by introducing molecular or crystalline symmetries in any lattice.

cond-mat.mtrl-sci↗

Tritium for Nanoscale Hydrogen Analysis by Atom Probe Tomography

Accurate nanoscale detection of hydrogen is essential for understanding hydrogen-related phenomena in materials, yet conventional tracing with deuterium is often complicated by residual background hydrogen. This study evaluates tritium as a highly resolvable isotopic marker for nanoscale hydrogen analysis in metals using atom probe tomography. Titanium was selected for its ability to incorporate hydrogen isotopes, providing a suitable platform for tritium detection. Time of flight secondary ion mass spectrometry and electron backscatter diffraction were performed prior to tritium charging to characterize the initial composition and microstructure. Atom probe tomography in laser mode before and after tritium charging, at three post-charging time intervals, enables tracking of tritium incorporation over time. Thermal desorption analysis confirmed the presence of tritium and complemented the secondary ion mass spectrometry measurements, highlighting the role of the surface oxide layer in modulating tritium release. While tritium, deuterium, and protium differ in their diffusion and trapping behavior, the distinct mass signal associated with tritium provides a practical advantage for resolving hydrogen at very low concentrations. This work serves as a fundamental benchmarking study for leveraging tritium and atom probe tomography as a combined tool for understanding hydrogen in materials, relevant for interpreting local processes such as hydrogen embrittlement.

cond-mat.mtrl-sci↗

Interfacial melting as a thermodynamic indicator of solid-state synthesizability

Computational materials discovery commonly ranks candidate materials by their thermodynamic stability on the formation energy convex hull, yet many predicted-stable phases resist synthesis. We propose that solid-state synthesizability through interfacial-melt-mediated routes requires an additional thermodynamic condition: the interfacial melt at the target composition must itself remain locally stable against spinodal decomposition. We examine this in the classical Fe--B system, where thermodynamically stable FeB$_4$ has been reported under high-pressure synthesis but not in low-pressure synthesis attempts. Using melt--quench molecular dynamics driven by a fine-tuned machine-learning interatomic potential, we find that, at ambient pressure, the B-rich interfacial melt near the FeB$_4$ composition develops a concave free-energy landscape, signaling a demixing instability that is corroborated by the concentration--concentration structure factor and correlated with low-energy icosahedral and pentagonal-pyramidal boron motifs. In contrast to FeB$_4$, metastable Fe$_3$B and Fe$_{23}$B$_6$ remain synthesizable because their corresponding melts are stable. Applied pressure introduces a convex $PV$ contribution that strongly suppresses this instability, reducing the curvature at the FeB$_4$ composition to within the uncertainty of our fit at 1800~K, consistent with the experimental synthesis boundary. Comparison with CrB$_4$ further shows that weaker melt instability correlates with easier experimental synthesis. Interfacial-melt stability, which atomistic simulations can assess via the low-$k$ concentration--concentration structure factor, is thus proposed as a practical thermodynamic screening descriptor of synthesizability for AI-assisted materials discovery.

cond-mat.mtrl-sci↗