More Like this

1. High-efficiency Pt75Au25-based spintronic terahertz emitters

   https://doi.org/10.1063/5.0304951  

   Shi, Wenlu; Nelson, Gene D; Wu, Han-Hsuan; Ju, Yiwei; Pan, Xiaoqing; Ho, Wilson; Krivorotov, Ilya N (February 2026, Applied Physics Letters)

   Spintronic terahertz emitters (STEs) generate broadband THz radiation via ultrafast spin–charge conversion in magnetic multilayers, offering spectral coverage beyond that of photoconductive antennas and nonlinear optical crystals. Here, we demonstrate STEs based on a PtxAu100−x alloy that achieve significantly higher THz output power than widely used Pt-based devices. Alloy composition and layer thickness tuning yield Pt75Au25 as the optimal alloy, providing a 30% increase in THz power in CoFeB/Pt75Au25 bilayer STEs compared to the optimized CoFeB/Pt reference STE. In W/CoFeB/Pt75Au25 trilayer STEs, we observe a 10% higher THz power than in the optimized W/CoFeB/Pt trilayer. The STE efficiency is reduced upon annealing for both Pt75Au25- and Pt-based STEs due to the formation of interfacial alloys. Our results establish Pt75Au25 as a promising platform for high-performance STEs, where its giant spin Hall effect significantly enhances efficiency over conventional Pt-based devices. 

   more » « less
2. Spintronic Pathways in a Nonconjugated Radical Polymer Glass

   https://doi.org/10.1002/adma.202406727  

   Tahir, Hamas; Flores‐Hansen, Carsten; Hsu, Sheng‐Ning; Liang, Zihao; Naga, Jayant; Dilley, Neil R; Savoie, Brett M; Boudouris, Bryan W (January 2025, Advanced Materials)

   Abstract Radical chemistries have attracted burgeoning attention due to their intriguing technological applications in organic electronics, optoelectronics, and magneto‐responsive systems. However, the potential of these magnetically active glassy polymers to transport spin‐selective currents has not been demonstrated. Here, the spin‐transport characteristics of the radical polymer poly(4‐glycidyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl) (PTEO) allow for sustained spin‐selective currents when incorporated into typical device geometries with magnetically polarized electrodes. Annealing thin films of PTEO above its glass transition temperature results in a giant magnetoresistance effect (i.e., an MR of ≈80%) at 4 K. Additionally, ferromagnetic resonance spin‐pumping results in a relatively large effective spin‐mixing conductance of 1.18 × 10¹⁹m⁻²at the NiFe/PTEO interface. Due to the large spin‐density and radical‐radical exchange interactions, there is effective propagation of pure spin currents through PTEO in the NiFe/PTEO/Pd multilayer devices. This results in the transport of spin current over long distances with a spin diffusion length of 90.4 nm. The spin diffusion length and spin mixing conductance values surpass those reported in inorganic and metallic systems and are comparable to conventional doped conjugated polymers. This is the first example of spin transport in a nonconjugated radical polymer, and these findings underscore the promising spin‐transporting potential of radical polymers. 

   more » « less
3. Spin splitting tunable optical band gap in polycrystalline GdN thin films for spin filtering

   https://doi.org/10.1103/PhysRevB.109.L060401  

   Vilela, G_L S; Stephen, G M; Gratens, X; Galgano, G D; Hou, Yasen; Takamura, Y; Heiman, D; Henriques, A B; Berera, G; Moodera, J S (February 2024, Physical Review B)

   Rare-earth nitrides, such as gadolinium nitride (GdN), have great potential for spintronic devices due to their unique magnetic and electronic properties. GdN has a large magnetic moment, low coercitivity and strong spin polarization suitable for spin transistors, magnetic memories and spin-based quantum computing devices. Its large spin splitting of the optical bandgap functions as a spin-filter that offers the means for spin-polarized current injection into metals, superconductors, topological insulators, 2D layers and other novel materials. As spintronics devices require thin films, a successful implementation of GdN demands a detailed investigation of the optical and magnetic properties in very thin films. With this objective, we investigate the dependence of the direct and indirect optical bandgaps (𝐸𝑔) of half-metallic GdN, using the trilayer structure AlN(10 nm)/GdN(t)/AlN(10 nm) for GdN film thickness t in the ranging from 6 nm to 350 nm, in both paramagnetic (PM) and ferromagnetic (FM) phases. Our results show a bandgap of 1.6 eV in the PM state, while in the FM state the bandgap splits for the majority (0.8 eV) and minority (1.2 eV) spin states. As the GdN film becomes thinner the spin split magnitude increases by 60%, going from 0.290 eV to 0.460 eV. Our results point to methods for engineering GdN films for spintronic devices. 

   more » « less
4. Solution‐Processed Spin‐Polarized Light‐Emitting Diodes of Colloidal Quantum Wells and Magnetic Nanoparticles

   https://doi.org/10.1002/adom.202502254  

   Delikanli, Savas; Bhattacharya, Arinjoy; Canimkurbey, Betul; Huai, Chang; Almutairi, Amani; Najafi, Arman; Korkut, Hilal; Shabani, Farzan; Isik, Furkan; Pientka, James; et al (March 2026, Advanced Optical Materials)

   Abstract Electrical injection of spin‐polarized carriers into semiconductors enables circularly‐polarized emission from spin‐polarized light‐emitting diodes (spin‐LEDs). The incredible level of tunability of magnetic and electronic properties in colloidal nanocrystals offers unprecedented opportunities for the modulation of polarization of light in solution‐processed spin‐LEDs based on magnetic nanoparticles unlike epitaxially grown spin‐LEDs restricted by a very limited range of materials for their exploitation, and solution‐processed spin‐LEDs based on chiral molecules, which do not allow the modulation of polarization in general. Here, it is shown that electrical injection of spin‐polarized electrons from magnetic Fe₃O₄nanoparticles into CdSe/CdZnS core/shell colloidal quantum wells (CQWs) in solution‐processed LEDs that allows for polarization modulation of electroluminescence. In this structure, a monolayer of face‐down oriented CQWs is deposited as an active layer to avoid polarization losses due to the hopping of the electrons between the CQWs before the radiative recombination process. In this solution‐processed spin‐LED, the circular polarization reaches 4.5% at 3 K and survives up to 100 K. A net circular polarization is observed at zero magnetic field up to 100 K because of the remnant magnetization of the Fe₃O₄nanoparticles. This new colloidal spin‐LED architecture presents significant prospects for future solution‐processed advanced opto‐spintronic devices. 

   more » « less
5. Schottky contacts to N-polar GaN with SiN interlayer for elevated temperature operation

   https://doi.org/10.1063/5.0083588  

   Khachariya, Dolar; Szymanski, Dennis; Reddy, Pramod; Kohn, Erhard; Sitar, Zlatko; Collazo, Ramón; Pavlidis, Spyridon (April 2022, Applied Physics Letters)

   In this Letter, we unveil the high-temperature limits of N-polar GaN Schottky contacts enhanced by a low-pressure chemical vapor deposited (LPCVD) SiN interlayer. Compared to conventional Schottky diodes, the insertion of a 5 nm SiN lossy dielectric interlayer in-between Ni and N-polar GaN increases the turn-on voltage ( V ON ) from 0.4 to 0.9 V and the barrier height ( ϕ B ) from 0.4 to 0.8 eV. This modification also reduces the leakage current at zero bias significantly: at room temperature, the leakage current in the conventional Schottky diode is >10 3 larger than that observed in the device with the SiN interlayer, while at 200 °C, this ratio increases to 10 5 . Thus, the rectification ratio (I ON /I OFF ) at ±1.5 V reduces to less than one at 250 °C for the conventional Schottky diode, whereas for SiN-coated diodes, rectification continues until 500 °C. The I–V characteristics of the diode with an SiN interlayer can be recovered after exposure to 400 °C or lower. Contact degradation occurs at 500 °C, although devices are not destroyed yet. Here, we report N-polar GaN Schottky contact operation up to 500 °C using an LPCVD SiN interlayer. 

   more » « less