http://irgu.unigoa.ac.in/drs/handle/unigoa/5 2026-11-05T06:47:07Z http://irgu.unigoa.ac.in/drs/handle/unigoa/8129 Structural and magnetic asymmetry at the interfaces of an Ag/57Fe/Ag trilayer studied using x-ray standing wave based techniques Priyadarsini, M.; SharanjeetSingh; Sergeev, I.; Leupold,O.; Gupta, A.; Carlomagno, I.; Reddy, V.R.; Priolkar, K.R.; DileepKumar Interfaces in magnetic multilayers play a decisive role in determining their structural and magnetic properties, which significantly impact the performance of the spintronic devices. This work investigates the bottom and top interfaces of a few-nanometer-thick sup(57)Fe layer in an Ag/sup(57) Fe/Ag trilayer. The subnanometer depth resolution was obtained using x-ray standing waves (XSWs) generated by an underlying [W/Si] sub(10) multilayer. Each interface was selectively probed by scanning the standing-wave antinodes across the trilayer by varying the x-ray incidence angle around the Bragg condition. Detailed depth-resolved structural and magnetic information was obtained by combining the x-ray fluorescence (XRF) with isotope-selective (sup(57) Fe) grazing-incidence nuclear resonance scattering (GINRS) under XSW conditions. The results reveal a pronounced asymmetry in the interfacial roughness; the sup(57) Fe-on-Ag interface exhibits a larger rms roughness of 9.7 plus minus 1.0 Angstrom, whereas the Ag-on- sup(57) Fe interface is comparatively smoother, with a roughness of 6.4 plus minus 1.0 Angstrom. Correspondingly, GINRS measurements probed distinct hyperfine fields at the two interfaces, consistent with the observed structural asymmetry. Temperature-dependent measurements reveal enhanced interfacial intermixing. Fe K-edge extended x-ray absorption fine structure spectroscopy combined with temperature-dependent magnetic measurements shows that annealing at 325 degrees C induces strong nanoscale intermixing, resulting in the formation of Fe nanoparticles embedded in Ag. These results demonstrate that XSW-assisted XRF and GINRS provide a powerful and interface-specific probe of buried structural and magnetic asymmetries, offering valuable insights for the design and optimization of spintronic multilayer nanostructures. 2026-01-01T00:00:00Z http://irgu.unigoa.ac.in/drs/handle/unigoa/8128 Effect of off-stoichiometry on structural, transport, and magnetic properties of altermagnetic CrSb Tiwari, A.; Babu, P.D.; Acet, M.; Priolkar, K.R.; Bhobe, P.A. We investigate the effects of Cr off-stoichiometry on the structural, magnetic, thermodynamic, and electrical transport properties of the antiferromagnetic compound CrSb. Single-phase hexagonal NiAs-type structure is stabilized only in the Cr-rich regime, where excess Cr atoms preferentially occupy the interstitial trigonal bipyramidal 2?d sites, as confirmed from the x-ray diffraction study. Synchrotron-based x-ray absorption fine-structure measurements reveal a progressive increase in local structural disorder with increasing Cr concentration, particularly within the Cr sublattice. Magnetization measurements show a pronounced low-temperature upturn in susceptibility and nonlinear field-dependent behavior, which can be consistently described by the formation of short-range magnetic clusters associated with interstitial Cr moments embedded in the antiferromagnetic CrSb matrix. Specific-heat measurements indicate a finite electronic density of states at the Fermi level with a nonmonotonic evolution of the Sommerfeld coefficient with Cr content, reflecting the interplay between electronic delocalization and disorder-induced localization. Electrical transport measurements confirm metallic conduction across all compositions and reveal the emergence of an antiferromagnetic gap at low temperatures with increasing Cr concentration. These results demonstrate a strong coupling between off-stoichiometry, local structural disorder, magnetic correlations, and charge transport in Cr sub(1+x)?Sb and establish controlled Cr occupancy as an effective route for tuning magnetic interactions and electronic responses relevant to altermagnetic systems. 2026-01-01T00:00:00Z http://irgu.unigoa.ac.in/drs/handle/unigoa/8127 Decoupling electronic and lattice contributions to martensitic transformation in Ni sub(2)Mn sub(1.5)Ga sub(0.5) Heusler alloys Manea, N.; Welter, E.; Priolkar, K.R. The interplay between electronic structure and lattice degrees of freedom governs martensitic transformations in Ni-Mn-based Heusler alloys, yet their relative contributions remain difficult to disentangle. Here, we address this issue through a systematic investigation of Ni sub(2)Mn sub(1.5)Ga sub(0.5-x)In sub(x) (0 less than or equal to x less than or equal to 0.5), where isoelectronic substitution of In for Ga enables isolation of lattice effects at nearly constant valence electron concentration (e/a approximately equal to 8). A pronounced and monotonic decrease in the martensitic transformation temperature (T sub(M)) is observed with increasing In content, despite negligible variation in e/a, indicating a non-electronic origin of the transformation suppression. On the other hand, a direct correlation between T sub(M) and lattice expansion and the bond-length difference Delta R = (R sub(Ni-Z)- R sub(Ni-Mn)) establishes local structural distortions as a key control parameter. These results are interpreted within a strain accommodation framework, wherein lattice expansion induced by larger In atoms progressively relieves internal strain, thereby reducing the elastic energy difference between austenite and martensite phases and suppressing the transformation. Magnetization measurements further indicate the emergence of frustrated magnetic states arising from competing exchange interactions in a structurally heterogeneous environment. These findings demonstrate that lattice-driven effects can dominate martensitic phase stability independently of electronic concentration and provide a pathway for tuning functional properties in Heusler alloys via controlled manipulation of local structure and strain. 2026-01-01T00:00:00Z http://irgu.unigoa.ac.in/drs/handle/unigoa/8126 Local atomic structure of molybdenum-based vacancy-ordered perovskites: A direct evidence of oxyhalide formation and selective doping Ghosh, R.; Dutta, S.; Joseph, I.M.; Roy, U.; Rathod, R.; Saha, D.; Priolkar, K.R.; Banerjee, R.; Santra, P.K. Doping in lead-free vacancy-ordered perovskites (A sub(2)BX sub(6)) is a primary strategy for modulating their optoelectronic properties; however, the precise local atomic arrangements and the feasibility of doping-induced structural transformations remain poorly understood, as global structural techniques often fail to capture local variations. In this work, utilizing extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional theory (DFT) calculations, we probe the local atomic structure of the Mo-based vacancy-ordered perovskite and demonstrate that the material preferentially adopts an oxyhalide configuration, identified as Cs sub(2)MoO sub(x)Cl sub(6-x) (1.3 less than x less than 1.5), which possesses a significantly more favorable formation energy than the pure halide phase. Attempts to drive a structural transition toward a double perovskite (Cs sub(2)AgBiCl sub(6)) via Ag sup(+)/Bi sup(3+) codoping revealed selective dopant incorporation. While Bi sup(3+) successfully substitutes for Mo within the octahedral environment-a process confirmed by EXAFS and supported by a high positive Bader charge transfer (+2.73 e)-Ag sup(+) incorporation is fundamentally hindered due to the unfavorably large ionic radius of Ag sup(+). At higher dopant concentrations, the system undergoes phase segregation into discrete Cs sub(2)MoO sub(x)Cl sub(6-x) and Cs sub(2)AgBiCl sub(6) phases rather than doping. This study establishes that understanding the local atomic coordination is indispensable for rational dopant engineering in low-dimensional halide systems where bulk structural techniques are insufficient. 2026-01-01T00:00:00Z