Synthesis and defect control of
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
<mml:mrow>
<mml:msub>
<mml:mi>Sr</mml:mi>
<mml:mn>2</mml:mn>
</mml:m
Aug 2026· PHYSICAL REVIEW MATERIALS· 0 citations· 40 references
Abstract
Sr
2
IrO
4
(Sr214) and related iridates have emerged as key platforms for fundamental correlated-electron physics and for potential applications such as magnonics. Here, we report the epitaxial growth of high-quality Sr214 thin films using reactive off-axis sputtering. Conventional pulsed-laser deposition of Sr214 suffers from limitations arising from the volatility and decomposition of iridates, which often result in parasitic Ruddlesden–Popper phases and iridium vacancies. By employing sputtering, we mitigate these issues and achieve stable growth conditions that allow precise mapping of the phase diagram. Systematic variation of the growth temperature reveals that Sr214 stabilizes within a window between
825
∘
C
and
1050
∘
C
, with optimal crystallinity and thickness obtained at
840
∘
C
. Raman spectroscopy provides sensitive diagnostics of iridium vacancies, with defect-induced phonon modes and peak intensity ratios correlating strongly with the
c
-axis lattice parameter. Our results establish reactive sputtering as a robust route for integrating Sr214 into oxide electronic and magnonic device architectures.
We report on the synthesis and characterization of
M
n
3
Ga
thin films with controlled phase and orientation using DC magnetron sputtering. High-quality Mn-deficient hexagonal
M
n
3
Ga
films with C-plane and M-plane orientations were achieved on various single-crystal substrates, and their structural properties were systematically investigated by x-ray diffraction. Magnetization, Hall effect, and neutron diffraction measurements confirm the formation of antiferromagnetic order below
T
N
=
460
–
470
K and reveal its characteristic magnetic behavior. A sizable anomalous Hall effect is observed coexistent with weak net magnetization, consistent with the 120° noncollinear spin structure. The ability to tune both the crystal phase (hexagonal vs tetragonal) and orientation through composition and thermal treatment provides a platform for exploring the intrinsic magnetic and topological properties of
M
n
3
Ga
, with promising implications for antiferromagnetic spintronic applications.
Q. Tao, A. Petruhins, R. Shu et al.· PHYSICAL REVIEW MATERIALS· 0 citations
In this work, we report the discovery of a new crystal structure on the Ge-rich side of the Pr-Ge binary phase diagram. Using a high-temperature flux technique, we grew single crystals of $Pr_9Ge_{16}$, which adopt a previously unreported orthorhombic $Fdd$2 structure type featuring ordered Ge vacancies. We present the anisotropic magnetic properties and identify the crystallographic $b$ axis perpendicular to the crystal plane as the magnetic easy axis. Temperature-dependent resistivity measurements reveal metallic behavior with a distinct anomaly at $T_{\mathrm{C}}$ = 14.3 K. Hall resistivity data indicate that electron-like carriers dominate, with a carrier concentration on the order of $10^{27}~\mathrm{m}^{-3}$. The magnetic order is readily suppressed by a magnetic field of approximately 0.4 T applied along the easy $b$ axis.
Jayashani S. T. Wickramasinghe, Melissa G. Anderson, Kelci Graville et al.· PHYSICAL REVIEW MATERIALS· 0 citations
Rutile
Sn
1
−
x
Ge
x
O
2
alloys are promising materials for high-power electronic applications due to their dopability and tunable ultrawide band gaps. We use first-principles density functional theory and statistical mechanics to investigate the crystallographic, electronic, and thermodynamic properties of rutile
Sn
1
−
x
Ge
x
O
2
alloys. We predict that the lattice parameters follow Vegard's law, while band gaps calculated with the hybrid HSE06 functional exhibit strong bowing, consistent with experiment. We also predict that the disordered phase has a large positive mixing enthalpy and a slight tendency for Ge-Sn clustering, indicated by weakly negative short-range order parameters. This large positive mixing enthalpy produces a miscibility gap with a critical temperature above 2300 K, implying that the high Ge and Sn solubilities observed in thin-film synthesis cannot be explained by the incoherent phase diagram alone. We demonstrate that coherency strain substantially alters phase stability. Calculations of the coherent spinodal show significant suppression of the miscibility gap, reducing the critical temperature to
≈
900
K
. These coherent phase boundaries could account for the experimentally observed high solubilities at typical growth temperatures. Our results indicate that coherency strain stabilizes these metastable alloys and enables band-gap engineering in this ultrawide-band-gap material system.
Yann L. Müller, Alp Umut Kurbay, Xiao Zhang et al.· PHYSICAL REVIEW MATERIALS· 0 citations
Low-spin excited states in $^{68}$Zn have been studied at the High Intensity Gamma-Ray Source (HI$\gamma$S) from the ground state up to the particle emission threshold using the nuclear resonance fluorescence technique (NRF) and the newly developed Clover Array. Low-spin levels were excited by linearly-polarized, $2.90 - 9.79$ MeV photon beams. Spin-parity quantum numbers as well as associated $M1$ and $E1$ decay strengths were determined for a large fraction of the 158 states observed. In addition, long-duration coincidence measurements at 9.46 and 9.79 MeV enabled the investigation of the level scheme near the ground state. The results have been interpreted with shell-model calculations using two different model spaces and several effective interactions often used to describe nuclei in this mass region. While the structure near the ground state can be understood in terms of excitations involving solely valence nucleons, core breaking is required to account for the evolution of the total $M1$ strength at excitation energies above $\sim5$ MeV.
S. R. Johnson, R. V. F. Janssens, B. Brown et al.· Physical Review C· 0 citations
Ferroelectric materials are a class of dielectrics that exhibit spontaneous polarization which can be reversed under an external electric field. The emergence of ferroelectric order in incipient ferroelectrics is a topic of considerable interest from both fundamental and applied perspectives. Despite evidence from first-principles calculations that strain triggers ferroelectricity in
KTaO
3
, conventional methods cannot reliably characterize the soft-mode dynamics that govern its ferroelectric behavior. In this study, we investigate the impact of in-plane uniaxial and biaxial strain, ranging from 0 to 1%, on pristine
KTaO
3
to explore its potential for ferroelectricity induction via inversion symmetry breaking. By integrating density-functional theory calculations with the stochastic self-consistent harmonic approximation assisted by on-the-fly machine learned force fields, we obtain accurate structural information and dynamical properties under varying strain conditions while incorporating higher-order anharmonic effects. Employing the Berry-phase method, we obtained the ferroelectric polarization of the strained structures over the entire temperature range up to 300 K. Our findings provide valuable insights into the role of strain in stabilizing ferroelectricity in
KTaO
3
, offering guidance for future experimental and theoretical studies on strain-engineered ferroelectric materials.
Yu Zhu, Luigi Ranalli, Taikang Chen et al.· PHYSICAL REVIEW MATERIALS· 0 citations
While $1/f$ noise is ubiquitous and has been found in various systems, its physics remains uncertain. From an analytical study of an ordinary diffusion equation, we find an additional example of the $1/f$ noise. The formula for this example, together with existing knowledge about scaling in fluid turbulence, implies a necessary and sufficient condition for the occurrence of any stationary $1/f$ noise. That is, the noise needs to be characterized by two constant frequencies of $f_{\rm low} \ll f_{\rm high}$. For a frequency range from $f = f_{\rm low}$ to $f_{\rm high}$, it is further needed that, except for the mean amplitude of the noise, there is no other constant parameter. Then, at $f_{\rm low} \ll f \ll f_{\rm high}$, the noise scales asymptotically as $1/f$. Being statistical and simple, our condition applies to any system and hence explains the ubiquity of the $1/f$ noise. It is also applicable to some systems with noise of $\alpha \ne 1.0$ for $1/f^{\alpha}$, via intermittency analogous to that of the turbulence.