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1. Spin Wave Excitation, Detection, and Utilization in the Organic‐Based Magnet, V(TCNE) _x (TCNE = Tetracyanoethylene)

   https://doi.org/10.1002/adma.202002663  

   Liu, Haoliang; Malissa, Hans; Stolley, Ryan_M; Singh, Jaspal; Groesbeck, Matthew; Popli, Henna; Kavand, Marzieh; Chong, Su_Kong; Deshpande, Vikram_V; Miller, Joel_S; et al (August 2020, Advanced Materials)

   Abstract Spin waves, quantized as magnons, have low energy loss and magnetic damping, which are critical for devices based on spin‐wave propagation needed for information processing devices. The organic‐based magnet [V(TCNE)_x; TCNE = tetracyanoethylene;x≈ 2] has shown an extremely low magnetic damping comparable to, for example, yttrium iron garnet (YIG). The excitation, detection, and utilization of coherent and non‐coherent spin waves on various modes in V(TCNE)_xis demonstrated and show that the angular momentum carried by microwave‐excited coherent spin waves in a V(TCNE)_xfilm can be transferred into an adjacent Pt layer via spin pumping and detected using the inverse spin Hall effect. The spin pumping efficiency can be tuned by choosing different excited spin wave modes in the V(TCNE)_xfilm. In addition, it is shown that non‐coherent spin waves in a V(TCNE)_xfilm, excited thermally via the spin Seebeck effect, can also be used as spin pumping source that generates an electrical signal in Pt with a sign change in accordance with the magnetization switching of the V(TCNE)_x. Combining coherent and non‐coherent spin wave detection, the spin pumping efficiency can be thermally controlled, and new insight is gained for the spintronic applications of spin wave modes in organic‐based magnets. 

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2. Investigation of the monopole magneto-chemical potential in spin ices using capacitive torque magnetometry

   https://doi.org/10.1038/s41467-022-31297-1  

   Anand, Naween; Barry, Kevin; Neu, Jennifer N.; Graf, David E.; Huang, Qing; Zhou, Haidong; Siegrist, Theo; Changlani, Hitesh J.; Beekman, Christianne (July 2022, Nature Communications)

   Abstract The single-ion anisotropy and magnetic interactions in spin-ice systems give rise to unusual non-collinear spin textures, such as Pauling states and magnetic monopoles. The effective spin correlation strength (J_eff) determines the relative energies of the different spin-ice states. With this work, we display the capability of capacitive torque magnetometry in characterizing the magneto-chemical potential associated with monopole formation. We build a magnetic phase diagram of Ho₂Ti₂O₇, and show that the magneto-chemical potential depends on the spin sublattice (αorβ), i.e., the Pauling state, involved in the transition. Monte Carlo simulations using the dipolar-spin-ice Hamiltonian support our findings of a sublattice-dependent magneto-chemical potential, but the model underestimates theJ_efffor theβ-sublattice. Additional simulations, including next-nearest neighbor interactions (J₂), show that long-range exchange terms in the Hamiltonian are needed to describe the measurements. This demonstrates that torque magnetometry provides a sensitive test forJ_effand the spin-spin interactions that contribute to it. 

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3. Spin wavepackets in the Kagome ferromagnet Fe ₃ Sn ₂ : Propagation and precursors

   https://doi.org/10.1073/pnas.2220589120  

   Lee, Changmin; Sun, Yue; Ye, Linda; Rathi, Sumedh; Wang, Kevin; Lu, Yuan-Ming; Moore, Joel; Checkelsky, Joseph G.; Orenstein, Joseph (May 2023, Proceedings of the National Academy of Sciences)

   The propagation of spin waves in magnetically ordered systems has emerged as a potential means to shuttle quantum information over large distances. Conventionally, the arrival time of a spin wavepacket at a distance,d, is assumed to be determined by its group velocity,v_g. Here, we report time-resolved optical measurements of wavepacket propagation in the Kagome ferromagnet Fe₃Sn₂that demonstrate the arrival of spin information at times significantly less thand/v_g. We show that this spin wave “precursor” originates from the interaction of light with the unusual spectrum of magnetostatic modes in Fe₃Sn₂. Related effects may have far-reaching consequences toward realizing long-range, ultrafast spin wave transport in both ferromagnetic and antiferromagnetic systems. 

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4. Bulk‐Rashba Effect with Suppressed Spin Relaxation in a Polar Phase of Bi _{1‐ x} In _{1+ x} O ₃

   https://doi.org/10.1002/adma.202504684  

   Kang, Deokyoung; Lu, Xue‐Zeng; Acharya, Megha; Husain, Sajid; Harris, Isaac; Behera, Piush; Lin, Ching‐Che; Banyas, Ella; Smith, Alex; Ricci, Francesco; et al (July 2025, Advanced Materials)

   Abstract The Rashba effect enables control over the spin degree of freedom, particularly in polar materials where the polar symmetry couples to Rashba‐type spin splitting. The exploration of this effect, however, has been hindered by the scarcity of polar materials exhibiting the bulk‐Rashba effect and rapid spin‐relaxation effects dictated by the D'yakonov–Perel mechanism. Here, a polar LiNbO₃‐typeR3cphase of Bi_1‐xIn_1+xO₃withx≈0.15–0.24 is stabilized via epitaxial growth, which exhibits a bulk‐Rashba effect with suppressed spin relaxation as a result of its unidirectional spin texture. As compared to the previously observed non‐polarPnmaphase, this polar phase exhibits higher conductivity, reduced bandgap, and enhanced dielectric and piezoelectric responses. Combining first‐principles calculations and multimodal magnetotransport measurements, which reveal weak (anti)localization, anisotropic magnetoresistance, planar‐Hall effect, and nonreciprocal charge transport, a bulk‐Rashba effect without rapid spin relaxation is demonstrated. These findings offer insights into spin‐orbit coupling physics within polar oxides and suggest potential spintronic applications. 

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5. Preparation of metrological states in dipolar-interacting spin systems

   https://doi.org/10.1038/s41534-022-00667-4  

   Zheng, Tian-Xing; Li, Anran; Rosen, Jude; Zhou, Sisi; Koppenhöfer, Martin; Ma, Ziqi; Chong, Frederic T.; Clerk, Aashish A.; Jiang, Liang; Maurer, Peter C. (December 2022, npj Quantum Information)

   Abstract Spin systems are an attractive candidate for quantum-enhanced metrology. Here we develop a variational method to generate metrological states in small dipolar-interacting spin ensembles with limited qubit control. For both regular and disordered spatial spin configurations the generated states enable sensing beyond the standard quantum limit (SQL) and, for small spin numbers, approach the Heisenberg limit (HL). Depending on the circuit depth and the level of readout noise, the resulting states resemble Greenberger-Horne-Zeilinger (GHZ) states or Spin Squeezed States (SSS). Sensing beyond the SQL holds in the presence of finite spin polarization and a non-Markovian noise environment. The developed black-box optimization techniques for small spin numbers (N ≤ 10) are directly applicable to diamond-based nanoscale field sensing, where the sensor size limitsNand conventional squeezing approaches fail. 

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