title: Quantum phase transition from superparamagnetic to quantum superparamagnetic state in ultrasmall Cd(1-x)Cr(II)(x)Se quantum dots?
abstract: Despite a long history of success in formation of transition-metal-doped quantum dots (QDs), the origin of magnetism in diluted magnetic semiconductors (DMSs) is yet a controversial issue. Cr(II)-doped II-VI DMSs are half-metallic, resulting in high-temperature ferromagnetism. The magnetic properties reflect a strong p-d exchange interaction between the spin-up Cr(II) t(2g) level and the Se 4p. In this study, ultrasmall (~3.1 nm) Cr(II)-doped CdSe DMSQDs are shown to exhibit room-temperature ferromagnetism, as expected from theoretical arguments. Surprisingly, a low-temperature phase transition is observed at 20 K that is believed to reflect the onset of long-range ordering of the single-domain DMSQD.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, USA.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Zheng
authors.forename: Pushpendra
authors.initials: P
authors.lastname: Kumar
authors.forename: Aaron
authors.initials: A
authors.lastname: Washington
authors.forename: Zhenxing
authors.initials: Z
authors.lastname: Wang
authors.forename: Naresh S
authors.initials: NS
authors.lastname: Dalal
authors.forename: Geoffrey F
authors.initials: GF
authors.lastname: Strouse
authors.forename: Kedar
authors.initials: K
authors.lastname: Singh
mesh_terms: D002104:Cadmium / Q000737:chemistry*; D002857:Chromium / Q000737:chemistry*; D008280:Magnetics; D044367:Phase Transition; D045663:Quantum Dots; D011789:Quantum Theory; D012643:Selenium / Q000737:chemistry*; D013696:Temperature
chemical_list: D002104:Cadmium; D002857:Chromium; D012643:Selenium