Collective Magnetic Behavior in Vanadium Telluride Induced by Self-Intercalation

Self-intercalation
of native magnetic atoms within the van der
Waals (vdW) gap of layered two-dimensional (2D) materials provides
a degree of freedom to manipulate magnetism in low-dimensional systems.
Among various vdW magnets, the vanadium telluride is an interesting
system to explore the interlayer order–disorder transition
of magnetic impurities due to its flexibility in taking nonstoichiometric
compositions. In this work, we combine high-resolution scanning transmission
electron microscopy (STEM) analysis with density functional theory
(DFT) calculations and magnetometry measurements, to unveil the local
atomic structure and magnetic behavior of V-rich V1+xTe2 nanoplates with embedded V3Te4 nanoclusters grown by chemical vapor deposition (CVD). The
segregation of V intercalations locally stabilizes the self-intercalated
V3Te4 magnetic phase, which possesses a distorted
1T′-like monoclinic structure. This phase transition is controlled
by the electron doping from the intercalant V ions. The magnetic hysteresis
loops show that the nanoplates exhibit superparamagnetism, while the
temperature-dependent magnetization curves evidence a collective superspin-glass
magnetic behavior of the nanoclusters at low temperature. Using four-dimensional
(4D) STEM diffraction imaging, we reveal the formation of collective
diffuse magnetic domain structures within the sample under the high
magnetic fields inside the electron microscope. Our results shed light
on the studies of dilute magnetism at the 2D limit and on strategies
for the manipulation of magnetism for spintronic applications.