Search

III−V based diluted magnetic semiconductor (DMS) nanoparticles of In(1-x)MnxP (x ≤ 0.0135) have been prepared by slow heating of the reagents in trioctylphosphine oxide (TOPO) or by high-temperature injection of reagents dissolved in trioctylphosphine (TOP) into hot TOPO. The materials were prepared using either Mn(II) or Mn(III) salts as dopants and the resulting nanoparticles have diameters ranging from 2.95 ± 0.39 to 4.77 ± 0.73 nm, as determined from transmission electron micrographs. Chemical analysis of surface-exchanged samples revealed the incorporation of Mn into the crystal lattice with up to 6 Mn atoms per 3.4-nm diameter particle, or the equivalence of ~10²⁰ Mn atoms/cm³ in a zinc blende bulk lattice. The InP:Mn nanoparticles exhibited a red shift in the room-temperature photoluminescence of 0.02−0.03 eV relative to that for pure InP nanoparticles. Electron paramagnetic resonance studies suggest that the Mn atoms mostly reside near the surface and are Mn²⁺, regardless of the oxidation state of the precursor. The magnetic susceptibility of surface-exchanged nanoparticles doped with Mn(III) exhibited a paramagnetic behavior with a magnetic moment of 5.9 μB/Mn atom, consistent with 5 unpaired spins (S = 5/2 state). The successful incorporation of isovalent Mn to produce Mn²⁺ with a corresponding hole may represent a valuable strategy for production of ferromagnetic DMS nanoparticles based on arsenide systems, where the hole is coupled to the metal center and delocalized through the pnictide framework.

Phase-pure FeP nanoparticles have been synthesized by the reaction of iron(III) acetylacetonate with tris(trimethylsilyl)phosphine at temperatures of 240−320 °C using trioctylphosphine oxide as a solvent and dodecylamine (DA), myristic acid (MA), or hexylphosphonic acid (HPA) as additional capping groups (ligands). The DA-capped particles prepared at 260 °C have an average diameter of 4.65 ± 0.74 nm with FeP being the only observed crystalline phase. Elemental analyses indicate a high percentage yield of FeP (85%) and are consistent with 12% TOPO incorporation in the product. The addition of MA has results similar to those of the addition of DA, whereas addition of HPA seems to inhibit crystallite growth, resulting in very small (ca. 1 nm) or amorphous particles that are difficult to isolate. Magnetic susceptibility data on DA-capped FeP suggest that the moments within each particle are coupled antiferromagnetically, at least over a short range; however, there is no evidence of a Néel transition, in contrast to bulk FeP. It is likely that the FeP particles produced by this route are too small (ca. 5 nm) relative to the magnetic cell (2.9 nm) for the onset of long-range helical antiferromagnetic order, even at low temperatures (5 K) and fields (0.010 T).