Anisotropy-induced quantum critical behavior of magnetite nanoparticles at low temperatures

Quantum Phase Transition from Superparamagnetic to Quantum Superparamagnetic State in Ultrasmall Cd1–xCr(II)xSe Quantum Dots?

“…The anomalous line broadening at ∼20 K is indicative of a magnetic phase transition within the sample and has been interpreted as a QPT behavior for ferrous oxides at the nanoscale. 35,36,68 Further insight into the phase transition requires investigation of the magnetization behavior (MÀH) for the sample. In Figure 4, the field-dependent magnetization is shown as a function of temperature.…”

“…35,68 Such quantum tunneling behavior in a QD has been described but is controversial. 35,36,67,68 Further studies are required to prove the presence of the QPT in the CdCrSe QDs. Further theoretical and experimental studies are needed to understand the observed phenomenon completely.…”

“…Whether the critical transition represents a transition from a superparamagnetic to a quantum-superparamagnetic state is not clear, but the data are consistent with reports of such behavior at the nanoscale and warrant further investigation. 35,36,68 ' ASSOCIATED CONTENT b S Supporting Information. TEM and size dispersity analysis of Cd 0.994 Cr 0.006 Se, energy splitting diagram for Cr(II), and temperature-dependent HF-EPR data at 324 GHz.…”

Quantum phase transition and Fermi liquid behavior inPd1−xNixnanoalloys

“…Although there exists another set of reports of magnetism in ultrafine nanoclusters of these alloys, including the vicinity of xc [17][18][19], the studies are focused merely on the formation of giant moments around Ni atoms and do not address the possibility of a QPT. On the other hand, there exist reports on QPTs in insulating [20,21] and semiconducting [22] nanoparticles, wherein a temperature-driven phase transition from a superparamagnetic to a quantum superparamagnetic state occurs under a magnetic field. These reports leave a scope to explore QPT in other nanoparticle systems including the Pd]_xNix alloys.…”

Quantum Tunneling of Magnetization in Ultrasmall Half-Metallic V3O4 Quantum Dots: Displaying Quantum Superparamagnetic State

“…That is to say, the SP disappear when the thermal energy cannot overcome the magnetic energy barrier. If the size further reduces to small enough, the QTMs take place as temperature further decreases: dramatic increase in surface to volume ratio causes strong surface anisotropic field, which provides channels for quantum tunneling between spin-glass and quantum paramagnet, thus one can re-observe the SP state even when the thermal energy is smaller than the barrier height and denote as QSP 14 15 offers a very exciting possibility for computers using mesoscopic magnets for memory 16 . Magnetic quantum tunneling in quantum dots is of fundamental importance, not only for potential information and computation application but also because it presents possibility to deal experimentally with a single quantum object of mesoscopic size.…”