Physica Status Solidi B: Basic Solid State Physics

Apostolov, Angel T.; Apostolova, Iliana N.; Wesselinowa, Julia M.

doi: 10.1002/pssb.202500411pmid: N/A

The ferroelectric, dielectric, and piezoelectric characteristics of ion‐doped BaTiO3 (BTO) have been investigated using the transverse Ising model in combination with Green's function technique. The results reveal that doping BTO at the Ba site with Bi or Pb ions leads to enhanced ferroelectric, dielectric, and piezoelectric responses. Moreover, both the Curie temperature and the electrostrictive coefficient exhibit increased values compared to undoped BTO. Doping effects at the Ti site have also been examined, as well as at Ba or/and Ti sites. Additionally, the Curie temperature is found to rise with Ca doping at the Ba site and with (Zn,Co) codoping at the Ba and Ti sites. These doping effects have been analyzed from a microscopic perspective. Importantly, it is demonstrated for the first time that a competition arises between the tunneling frequency and the exchange interaction, attributable to differences in ionic radii and atomic mass between the dopant and host ions. The observed enhancements in the piezoelectric and ferroelectric properties of doped and codoped BTO highlight their significant potential for use in sensor and piezoelectric device applications.

Mahepal, Nisha; Akhani, Trilok; Solanki, Mitesh

doi: 10.1002/pssb.202500453pmid: N/A

A comprehensive first‐principles study has been conducted on the nitride perovskite SrTcN3, focusing on its structural, electronic, thermal, optical, phonon, and mechanical properties. SrTcN3 crystallises in a monoclinic phase with corner‐sharing TcN6 octahedra and demonstrates thermodynamic and dynamic stability. The Goldschmidt tolerance factor ∼0.98 and elastic constants confirm mechanical robustness. Electronic structure analysis reveals a semiconducting nature, featuring strong Tc 4d–N 2p hybridisation. High electrical conductivity and moderate Seebeck coefficients lead to a promising power factor. Optical properties include a high refractive index, strong absorption, and a static dielectric constant. Phonon dispersion analysis confirms the absence of imaginary modes, indicating dynamic stability, with a high Debye temperature. The combination of mechanical robustness, high Debye temperature, favourable electronic transport behaviour, strong optical absorption, and notable dielectric response positions SrTcN3 as a theoretically promising multifunctional material, supporting further exploration for high‐temperature semiconducting environments, radiation‐tolerant platforms, and concept‐level dielectric or photonic applications.

Uedono, Akira; Iguchi, Hiroko; Horita, Masahiro; Suda, Jun; Shima, Kohei; Chichibu, Shigefusa F.; Ishibashi, Shoji

doi: 10.1002/pssb.202500409pmid: N/A

Annealing behaviors of vacancy‐type defects in low‐dose ion‐implanted GaN are studied by positron annihilation. N+, Al+, and Si+ ions are implanted with a dose of 1 × 1012 cm−2. For Al‐ and Si‐implanted GaN after annealing at 1100 °C, the depth profiles of the net donor concentration (ND) are close to those for implanted impurities, but ND is 2–3 times higher than Al or Si concentrations. ND of N‐implanted GaN is higher than that of an unimplanted sample but is lower than that of the Al‐ and Si‐implanted samples. The origin of donor‐like defects introduced by ion implantation is expected to be N‐vacancy‐related defects. A comparison between depth profiles of vacancy‐type defects and ND reveals that Ga‐vacancy (VGa)‐type defects play a significant role in the annealing behavior of ND. Photoexcitation of VGa‐type defects and their electron detrapping phenomena are also studied.

Bharati, Maroj; Singh, Vikram; Kripal, Ram

doi: 10.1002/pssb.202500578pmid: N/A

Computational modeling of the axial zero field splitting and crystal‐field energy levels for Fe3+ doped YPO4 single crystals is performed utilizing the superposition model and perturbation theory to calculate the crystal field parameters and zero‐field splitting parameter. A good agreement between the experimental value and the theoretical axial zero‐field splitting parameter D is obtained. This confirms the experimental conclusion that Fe3+ ions replace Y3+ ions in single crystal of YPO4. The crystal field parameters and the crystal field analysis (CFA) package are used to calculate the optical spectra of the Fe3+ doped YPO4 crystal. The empirical and computed CF energy levels are mutually consistent. Thus, the experimental result is well supported by the theoretical analysis.

Jafarpisheh, Shaham; Volmer, Frank; Wang, Zhiwei; Canto, Bárbara; Ando, Yoichi; Stampfer, Christoph; Beschoten, Bernd

doi: 10.1002/pssb.202500313pmid: N/A

The spin‐polarized surface states in topological insulators offer unique transport characteristics that make them distinguishable from trivial conductors. Herein, the impact of these surface states in the topological insulator BiSbTeSe2 is detected by electrical means using a nonlocal (NL) transport configuration with ferromagnetic Co/Al2O3 electrodes. It is shown that the NL measurement allows probing of the surface currents flowing along the whole surface, i.e., from the top along the side to the bottom surface and back to the top surface along the opposite side. Increasing the temperature increases the interaction between bulk and surface states, which shortens this NL current path along the surface and hence leads to a complete disappearance of the NL signal at around 20 K. Interestingly, it is observed that the ratio between spin signal to background signal is much larger in the NL geometry compared to the local one. Given that the observed ratio in the NL geometry aligns well with expectations for spin‐polarized surface states, the findings suggest that an as‐yet unresolved mechanism diminishes the spin signal in the local geometry.

Li, Pengcheng; Liu, Zhixu; Liu, Yaxuan; Wen, Xin; Li, Zijian; Zhou, Wei; Wang, Shouyu; Liu, Weifang

doi: 10.1002/pssb.202500389pmid: N/A

With excellent optoelectronic behavior, organic‐inorganic hybrid perovskites have become leading contenders in the development of future photovoltaic and optoelectronic devices. Herein, two new lead‐free, quasi‐0D OIHPs, (C6H16N)2ZnI4 and (C6H16N)2CdI4, are synthesized, and both crystallize in the monoclinic system (P21/n space group) as confirmed via single‐crystal X‐ray diffraction analysis. Optical bandgaps are measured to be 4.595 eV for (C6H16N)2ZnI4 and 4.255 eV for (C6H16N)2CdI4, which align well with those from first‐principles calculations. Photoluminescence studies on (C6H16N)2ZnI4 and (C6H16N)2CdI4 show peaks at 393 and 382 nm, respectively, which are attributed to self‐trapped exciton (STE) transitions induced by lattice distortion. Notably, (C6H16N)2CdI4 exhibits unusual blue emission (quantum yield: 1.41%, lifetimes: 168.5 ps), while (C6H16N)2ZnI4 shows blue luminescence with enhanced efficiencies (quantum yields: 19.64%, lifetimes: 473.7 ps). These findings broaden the application prospects of 0D OIHP materials in renewable energy and photonics.

Bauden, Cecilia; Haag, Justus; Mendez, Alvaro; Munnik, Frans; Ganss, Fabian; Wennberg, Ambiörn; Fernandez, Ivan; Kaban, Ivan; Parala, Harish; Devi, Anjana; Krause, Matthias

doi: 10.1002/pssb.202500625pmid: N/A

The formation of the transparent conductive oxide SnO2:Ta by reactive direct‐current magnetron sputtering at a low temperature of 225°C was studied as a function of the oxygen flow rate using a pilot‐scale setup. Beginning with a mixture of β‐Sn and SnO as majority phases and minority fractions of Sn3O4 and SnO2 at very low O2 flows, up to the formation of phase‐pure rutile‐type SnO2:Ta at higher flow rates, a systematic evolution of the phase structure is observed. The SnO2:Ta (0.70 at.% Ta) film grown at optimized flow conditions exhibits a transmittance of >80% from 500 to 2500 nm and a specific resistivity of 0.3 Ω cm. While the transmittance is competitive, the resistivity is in the upper range of that reported for low‐temperature‐deposited SnO2:Ta films in research lab studies. Based on X‐ray diffraction, Raman spectroscopy, optical spectroscopy, and X‐ray photoelectron spectroscopy, we conclude that the small crystallite size, microstrain, and point defects caused by the low growth temperature might prevent charge carrier activation, even though the Ta dopant is incorporated as Ta5+ in the rutile‐type SnO2 lattice.

Dev, Jai; Kumar, Naveen; Singh, Sandeep; Singh, Surinder Pal; Kushwaha, Pallavi

doi: 10.1002/pssb.202500417pmid: N/A

The magnetic properties of MnZnSbxGe1−x single crystals (x = 0, 0.05, 0.10, and 0.15) are systematically studied to explore their magnetocaloric behavior. All compositions exhibit a paramagnetic‐to‐ferromagnetic transition near room temperature. A notable magnetic‐field‐induced first‐order magnetic phase transition is observed at ≈155 K (Tt) for x = 0.05, accompanied by a hysteresis width of ≈9 K, attributed solely to Ge substitution at Sb sites. The magnetic entropy change (ΔSM(T,H)), calculated using the Maxwell relation at the Curie temperature (TC ≈ 315 K), is −0.55 J kg−1K−1 for x = 0 and −0.49 J kg−1K−1 for x = 0.05 under a 1.2 T field, indicating a conventional magnetocaloric effect. Interestingly, for x = 0.05 at Tt ≈ 155 K, ΔSM(T,H) reaches +0.22 J kg−1K−1, marking an inverse magnetocaloric effect due to magnetic phase coexistence and structural coupling. To support the experimental observations, the magnetic entropy change ΔSM(T,H) is theoretically analyzed using Landau theory, and critical parameters are determined to identify the nature of magnetic interactions driving the transition. These results on dual‐action capability make MnZnSbxGe1−x a highly promising candidate for next‐generation magnetic refrigeration technologies.

Kumar, Pardeep; Das, Priya; Kuanr, Bijoy Kumar; Patnaik, Satyabrata

doi: 10.1002/pssb.202500233pmid: N/A

Ferrimagnetic spinel materials of formula AB2X4, where A and B are transition metals and X is oxygen or sulfur, hold promise for the realization of multiferroic characteristics. Herein, synthesis of spinel CoMn2O4 is reported and its magnetic, dielectric, and ferroelectric aspects and their correlations are explored. Polycrystalline CoMn2O4 is synthesized by using the conventional solid‐state method. The X‐ray diffraction and Raman spectroscopy confirm the phase purity of the synthesized compound. The crystal structure is identified with tetragonal symmetry (I41/amd space group). DC magnetization measurements indicate two magnetic transitions: one at temperature T 1 ≈ 186 K, followed by another Yafet–Kittel ferrimagnetic transition at T 2 ≈ 86 K. A frequency‐independent anomaly in the temperature‐dependent dielectric permittivity is observed near the low magnetic ordering temperature (T 2). This reflects the possibility of the correlation between lattice dynamics and spin ordering in spinel CoMn2O4. A substantial exchange bias is also observed below T 2 ≈ 86 K. The change in dielectric permittivity in the presence of applied magnetic field follows the square of the magnetization dependence, which is consistent with Ginzburg–Landau theory. However, the detailed pyroelectric current measurements reveal the absence of intrinsic ferroelectric order.

Merrad, Amel; Bouchenafa, Halima; Benichou, Boucif

doi: 10.1002/pssb.202500364pmid: N/A

The present study investigates the structural, dynamical, mechanical, electronic, optical, and thermoelectric properties of the double perovskites Rb2NaTlX6 (X = Br, Cl) using density functional theory. Phonon dispersion calculations confirm that the compounds are mechanically robust and dynamically stable. Analysis of the electronic band structure reveals direct band gaps in both Rb2NaTlBr6 and Rb2NaTlCl6. These gaps increase significantly when the modified Becke–Johnson approximation (mBJ) is used instead of the standard PBE−generalized gradient approximation (GGA) approximation. For Rb2NaTlBr6, for example, the band gap rises from 0.76 eV (GGA) to 1.64 eV (mBJ) and then to 2.95 eV with the inclusion of spin‐orbit coupling (SOC). Similarly, Rb2NaTlCl6's band gap increases from 1.70 eV (GGA) to 4.46 eV (mBJ) and then slightly decreases to 4.43 eV when mBJ‐GGA + SOC is included. The compounds also demonstrate strong optical absorption in the visible spectrum and favorable thermoelectric performance, suggesting their potential for use in energy conversion applications.