While broadband electromagnetic (EM) loss mechanisms have critical implications for both electromagnetic absorbers and magnetic hyperthermia, integrating diverse loss channels into single material architecture remains a key challenge for next-generation multifunctional composites. Herein, we introduce carbon confinement of Cobalt Ferrite nanoparticles (CFO@C) as a design principle to simultaneously address the performance-processability trade-off for broadband functionality. Mesoporous activated carbon acts as a reactive template that constrains CFO nanoparticle growth (), mitigates agglomeration, and provides conductive pathways for complementary dielectric response (epsilon). Static magnetometry reveals complex magnetic behavior driven by coexisting hard and soft phases, which is quantitatively resolved using Voigt-profile deconvolution of the wasp-waisted hysteresis loops, enabling phase-resolved analysis of reversal processes. Ferromagnetic Resonance (18-30 GHz) reveals a stable g-factor and large damping (alpha = 0.14) indicative of efficient GHz-frequency energy dissipation governed by spin-lattice relaxation. Low-frequency magnetic hyperthermia validates linear-response relaxation as the dominant loss channel under physiological field conditions (310 kHz, 400-800 Oe). These results establish CFO@C as a multifunctional nanocomposite that unifies broadband EM dissipation with efficient low-frequency heating, establishing the pathway for mu - epsilon co-design in frequency-adaptive materials relevant to printed electronics, EMI mitigation, and magnetically driven functional devices.

Iron oxides are one of the oldest magnetic systems in history and have been studied extensively due to their phase-tunable magnetic and electronic properties. The combination of ferrimagnetic half-metallic magnetite (Fe3O4) with antiferromagnetic insulating hematite (α-Fe2O3) forms a so-called biphase iron oxide (BPIO) system that exhibits highly tunable magnetic and spin-transport properties in terms of phase and volume fraction. In this work, we report the interfacial physics between variations of these iron oxide phases with graphene (Gr) on magnetotransport in these heterostructures. Our experiments reveal that the inclusion of graphene in these heterostructures induces an inversion in the sign of magnetoresistance at finite temperatures. We explain this observation with an effective percolative transport model. Interestingly, the switching temperature and the sharpness of the transition can be further tuned by varying the phase volume fractions of the iron oxide layer and the crystallinity. The BPIO films, which grow naturally on Si substrates, exhibit the highest switching temperature. Our observations underscore the ability to induce magnetoresistive switching in abundant iron oxide grown on cost-effective, CMOS-compatible substrates by including a single layer of Gr, which has potential applications in modern devices and neuromorphic computing.

The worldwide expedition for sustainable energy resources and clean electrical energy harvesting from renewable thermal energy has led to the dawn of spincaloritronics, a vast field that amalgamates spin transport and thermoelectricity. The anomalous Nernst effect (ANE) is one of the many branches of spincaloritronics which is usually observed in metallic and semiconducting magnetic materials. This effect makes use of the spin degree of freedom of an electron in those materials in addition to its charge to harvest electrical energy from renewable thermal energy. The ANE has recently attracted the attention of the spincaloritronics community as ANE-based thermoelectric generators have demonstrated superior performance and advantages over conventional Seebeck effect-based thermoelectric generators. Magnetic Heusler alloys with high Curie temperatures and large spin polarizations along with tunable magnetic and magnetotransport properties have shown emergent potential for room temperature ANE-based thermopile device applications. Particularly, topological Heusler alloys, such as Co2MnGa, which exhibits large intrinsic Berry curvatures at the Fermi energy, have demonstrated the largest anomalous Nernst conductivities reported to date at room temperature amongst all conventional magnetic materials. Unlike prior reviews, which have focused on specific subclasses, our article offers a broader and more inclusive survey. In this article, we aim to review recent progress in the study of the ANE across a broad spectrum of magnetic Heusler alloys, including full, quaternary, and half Heusler compounds, and explore their potential for room-temperature ANE-based thermoelectric device applications as well as propose potential strategies for enhancing ANE in these magnetic Heusler alloys.

Cobalt ferrite (CFO), despite its prospect in high-frequency applications, is limited by its narrow magnetic loss bandwidth, which significantly restricts its potential in broadband electromagnetic shielding. Here, we synthesize a Co-CoFe2O4-based nanocomposite system (Co-CFO NC) to expand the potential applications of the traditionally hard inverse spinel ferrite, CFO, via the inclusion of magnetically soft, high saturation magnetization Co. To confirm the morphology, chemical composition, and crystal structures, we employed a combination of analytical techniques including transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results suggest that the synthesized nanostructures are highly crystalline with the elemental Co effectively integrated into the CFO particles, resulting in a cohesive composite system. Static and dynamic magnetic measurements were performed, which indicate robust magnetic ordering across a broad frequency range, underscoring the potential applicability of these nanostructures in high-frequency applications. Ferromagnetic resonance (FMR) studies reveal broadband resonance dispersion across 20-36 GHz, with a giant damping parameter indicative of strong energy dissipation. These properties, coupled with exchange-mediated interfacial coupling (g ave approximate to 1.88), probe the frequency-dependent permeability critical for skin depth control ( ( rho omega mu ) ) , demonstrating the system's potential for GHz-range electromagnetic shielding. Low-temperature magnetic exchange bias is observed. The respective contributions from the magnetically hard and soft phases were deconvoluted to determine the intrinsic and extrinsic magnetic properties. Additionally, a parameter, denoted as the exchange dispersion (delta), is introduced, which quantifies interfacial coupling dynamics during reversal, linking quasi-static and GHz-scale behavior. These results emphasize the potential of the inclusion of elemental Co in the Co-CFO composite system to tune the magnetic properties for high-frequency electromagnetic shielding, where the hybrid hard/soft phases enable broadband microwave absorption and EMI shielding in next-generation communication devices.

We report on the anomalous transverse magnetothermoelectric properties of the topological spin semimetallic equiatomic quaternary Heusler alloys (EQHAs) FeCrRhSi and FeCrRhGe over a wide temperature range between 130and295K. Magnetic measurements reveal ferromagnetic behavior above room temperature with high Curie temperatures (>400K) in these samples, where energetically competing ferromagnetic (FM) and antiferromagnetic (AFM) phases coexist at low temperatures, giving rise to field-induced metamagnetic transitions. The electrical resistivity of both samples exhibits semimetallic characteristics throughout the measured temperature range, with low-temperature resistivity upturns driven by Kondo-like scattering. Throughout this range, the longitudinal Seebeck coefficient is negative in sign for both FeCrRhSi and FeCrRhGe, indicating that electrons are the majority carriers for thermally driven charge transport. Notably, both samples exhibit giant values of the anomalous Nernst coefficient ((ANE)) at room temperature, with (ANE) values of (0.272 +/- 0.02)mu VK-1 for FeCrRhSi and (0.295 +/- 0.02)mu VK-1 for FeCrRhGe. These values are nearly three times larger than those reported for other EQHAs in the literature. An in-depth analysis reveals that intrinsic Berry curvature drives such large anomalous Nernst effects (ANEs) in our EQHAs. We show that in these samples, the contribution of the transverse thermoelectric conduction to the observed large ANE dominates over that of anomalous Hall effect acting on the charge carrier flow driven by the longitudinal Seebeck effect. The ratio of the anomalous off-diagonal transverse thermoelectric conductivity () to the anomalous Hall conductivity ((AHE)) |/(AHE)| lies between 0.2((/)) and ((/)) at room temperature, further highlighting the intrinsic Berry curvature as the underlying physical origin of the observed large ANEs.

The magnon propagation length, ⟨ξ⟩, of a ferro-/ferrimagnet (FM) is one of the key factors that controls the generation and propagation of thermally driven magnonic spin current in FM/heavy metal (HM) bilayer based spincaloritronic devices. For the development of a complete physical picture of thermally driven magnon transport in FM/HM bilayers over a wide temperature range, it is of utmost importance to understand the respective roles of temperature-dependent Gilbert damping (α) and effective magnetic anisotropy (Keff) in controlling the temperature evolution of ⟨ξ⟩. Here, we report a comprehensive investigation of the temperature-dependent longitudinal spin Seebeck effect (LSSE), radio frequency transverse susceptibility, and broad-band ferromagnetic resonance measurements on Tm3Fe5O12 (TmIG)/Pt bilayers grown on different substrates. We observe a significant drop in the LSSE voltage below 200 K independent of TmIG film thickness and substrate choice. This is attributed to the noticeable increases in effective magnetic anisotropy field, HKeff (∝Keff) and α that occur within the same temperature range. From the TmIG thickness dependence of the LSSE voltage, we determined the temperature dependence of ⟨ξ⟩ and highlighted its correlation with the temperature-dependent HKeff and α in TmIG/Pt bilayers, which will be beneficial for the development of rare-earth iron garnet based efficient spincaloritronic nanodevices.

Conventionally, the modulation of the intrinsic Weyl nodes in Weyl semimetals is challenging, due to topological protection. Here we report the structural dependence of the Weyl nodes in a Co2MnGa Heusler thin film via a temperature-dependent tetragonal distortion. The ability to manipulate these Weyl nodes allows for the control of the intrinsic electromagnetic properties. Temperature-dependent x-ray diffraction (XRD) measurements identify a compressive tetragonal distortion with decreasing temperature from 300 to 20 K. The calculated Weyl properties can be directly compared with experimental parameters through the temperature-dependent XRD measurements which show the intrinsic correlation between Weyl properties and important magnetic parameters. The microscopic momentum space properties of Weyl nodes such as the distance (dW), solid angle (QW), tilt (cpW), and nodal point energy (EW) directly affect the macroscopic observable properties such as exchange stiffness (A), magnetization (M), and effective anisotropy field (HKeff), as shown via structure-dependent density functional theory calculations. These predictions are experimentally observed as large variations in the bulk magnetization and effective anisotropy field as a function of temperature. These results highlight a unique degree of freedom in the control of macroscopic magnetic properties via the modulation of the intrinsic properties of Weyl nodes through structural distortions.

Rare-earth iron garnets (REIGs) are the benchmark systems for magnonics, including the longitudinal spin Seebeck effect (LSSE). While most research has focused on single-crystalline REIGs on complimentary garnet substrates, moving to more, cost-effective complementary metal-oxide semiconductor (CMOS)-compatible substrates is important to integrate REIG thin films with existing technology. In this regard, we grow a 130 nm-thick polycrystalline gadolinium iron garnet (GdIG) film on the Si/SiO2 substrate and investigate the temperature-dependent LSSE. Interestingly, the polycrystalline GdIG film exhibits perpendicular magnetic anisotropy (PMA) at room temperature which is induced by tensile in-plane (IP)-strain originating from the thermal-expansion mismatch between the GdIG film and the substrate during rapid thermal annealing. Further, a spin-reorientation transition from the out-of-plane IP direction below TS = 180 K is observed. Additionally, the film reveals a magnetic compensation temperature, TComp, of ≈240 K. The LSSE voltage not only demonstrates a sign-inversion around TComp, but also shows noticeable changes around TS. As compared to a single-crystalline GdIG film, the lower LSSE voltage for the polycrystalline GdIG is attributed to the higher effective magnetic anisotropy and enhanced magnon scattering at the grain boundaries. Our study not only paves the way for the cost-effective growth of CMOS-compatible REIG-based systems with PMA for magnonic memory and information processing applications, but also highlights the fact that the spincaloritronic and spin-insulatronic properties of the polycrystalline REIGs follow those of their single-crystalline counterparts with reduced spin-to-charge conversion efficiency through LSSE which can be tuned further by controlling the average gran size and interface engineering.

Here we report on a comprehensive investigation of transverse magnetothermoelectric properties of the equiatomic quaternary Heusler alloys CrRu X Ge ( X = Co and Mn). Magnetic measurements reveal the presence of a glassy magnetic ground state owing to the energetically competing ferromagnetic and antiferromagnetic phases in CrRuCoGe at low temperatures, whereas CrRuMnGe exhibits soft ferromagnetic behavior with a weak martensitic transformation close to room temperature. The temperature -dependent anomalous Nernst coefficient ( S ANE ) of CrRuMnGe shows noticeable changes around the martensitic transformation. While CrRuCoGe exhibits positive S ANE , CrRuMnGe exhibits negative S ANE throughout the measured temperature range. We demonstrate that the contribution of the anomalous transverse thermoelectric conduction dominates that of the anomalous Hall effect acting on the thermally generated carrier flow induced by the longitudinal Seebeck effect, which gives rise to the opposite polarity of S ANE in these two alloys. Our detailed analysis indicates that the origin of the observed anomalous Nernst effect (ANE) in both of these alloys is dominated by the asymmetric skew scattering of charge carriers in the measured temperature regime. The sign change and tunability of ANE presented in this study provide a step forward toward the development of ANE-based efficient thermopile devices operating at room temperature utilizing the equiatomic quaternary Heusler alloys.

The recent discovery of long-range magnetic ordering in two-dimensional (2D) van der Waals solids [1], [2] has reignited the research efforts in 2D materials due to its potential for applications in spintronics and quantum technology. Most practical applications will require 2D materials displaying magnetism at room temperature. [3] –[8] 2D semiconductor transition metal dichalcogenides (TMDs), like the MX 2 family [where M=Mo, W, Re and X=S, se or Te], containing nonmagnetic elements are, in general, nonmagnetic. Nevertheless, diverse approaches have been explored to induce magnetism in these 2D-TMDs; for instance, introducing vacancies, [9] magnetic adatoms, [10] Substitutional doping, [5] –[8], [11] functionalization [10] and edge effects. [12] –[14] substitutional doping in TMDs, with different magnetic and non-magnetic atoms such as V, Co, Cr and Fe, has also been proven to induce composition dependent room-temperature magnetism. [5] –[8], [15] –[18]

The magnon propagation length, (MPL) of a ferro/ferrimagnet (FM) is one of the key factors that controls the generation and propagation of thermally-driven spin current in FM/heavy metal (HM) bilayer based spincaloritronic devices. Theory predicts that for the FM layer, MPL is inversely proportional to the Gilbert damping (alpha) and the square root of the effective magnetic anisotropy constant (K_eff). However, direct experimental evidence of this relationship is lacking. To experimentally confirm this prediction, we employ a combination of longitudinal spin Seebeck effect (LSSE), transverse susceptibility, and ferromagnetic resonance experiments to investigate the temperature evolution of MPL and establish its correlation with the effective magnetic anisotropy field, H_K^eff (proportional to K_eff) and alpha in Tm3Fe5O12 (TmIG)/Pt bilayers. We observe concurrent drops in the LSSE voltage and MPL below 200 K in TmIG/Pt bilayers regardless of TmIG film thickness and substrate choice and attribute it to the noticeable increases in H_K^eff and alpha that occur within the same temperature range. This study not only highlights the ability to manipulate MPL by controlling H_K^eff and alpha in FM/HM based spincaloritronic nanodevices, but also shows that the tuning of alpha is more effective than H_K^eff in controlling MPL and, hence, the spincaloritronic efficiency.

The recent discovery of long-range magnetic ordering in two-dimensional (2D) van der Waals solids [1], [2] has reignited the research efforts in 2D materials due to its potential for applications in spintronics and quantum technology. Most practical applications will require 2D materials displaying magnetism at room temperature. [3] –[8] 2D semiconductor transition metal dichalcogenides (TMDs), like the MX <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> family [where M=Mo, W, Re and X=S, se or Te], containing nonmagnetic elements are, in general, nonmagnetic. Nevertheless, diverse approaches have been explored to induce magnetism in these 2D-TMDs; for instance, introducing vacancies, [9] magnetic adatoms, [10] Substitutional doping, [5] –[8], [11] functionalization [10] and edge effects. [12] –[14] substitutional doping in TMDs, with different magnetic and non-magnetic atoms such as V, Co, Cr and Fe, has also been proven to induce composition dependent room-temperature magnetism. [5] –[8], [15] –[18]

Engineeringof interfacial magnetic properties provides an extraedge in designing heterostructures with desired properties for spintronicsand spincaloritronics, without drastically changing the structureof the neighboring nonmagnetic material. Here, we report on the surfacetermination-enhanced magnetic properties of the ferrimagnetic insulator(FMI) nickel ferrite (NFO) with the inclusion of graphene (Gr) andmonolayer hexagonal boron nitride (hBN). Depth-dependent X-ray photoelectronspectroscopy (XPS) measurements reveal the presence of a layer ofadsorbed oxygen at the NFO/Gr and NFO/hBN interfaces. Magnetometryand transverse susceptibility measurements indicate that the inclusionof monolayer Gr increases the saturation magnetization (M (s)) by 40% and decreases the effective magnetic anisotropyby 50% across 5 K <= T <= 300 K. A similarbut less pronounced effect is observed for the inclusion of hBN. Densityfunctional theory calculations further indicate that the increasein M (S) due to the inclusion of Gr or hBNarises on oxygen-terminated NFO, as observed in XPS measurements.These results present ways for engineering strong interfacial magneticeffects in FMI/2D nanomaterial systems, controlling magnetism by surfacetermination, and developing advanced spinterfaces for applicationsin spincaloritronics and spin insulatronics.

We report on a systematic investigation of the longitudinal spin Seebeck effect (LSSE) in a GGG(Gd3Ga5O12)/GdIG(Gd3Fe5O12)/Pt film series exhibiting an in-plane magnetic easy axis with a compensation temperature (T_Comp) that decreases from 270 to 220 K when decreasing GdIG film thickness from 272 to 31 nm, respectively. For all the films, the LSSE signal flips its sign below T_Comp. We demonstrate a universal scaling behavior of the temperature dependence of LSSE signal for our GdIG films around their respective T_Comp. Additionally, we demonstrate LSSE in a 31 nm GdIG film grown on a lattice-mismatched GSGG (Gd3Sc2Ga3O12) substrate that exhibits an out-of-plane magnetic easy axis at room temperature. However, this sample reveals a spin reorientation transition where the magnetic easy axis changes its orientation to in-plane at low temperatures. We observed a clear distinction in the LSSE signal for the GSGG/GdIG(31 nm)/Pt heterostructure, relative to GGG/GdIG(31nm)/Pt showing an in-plane magnetic easy axis. Our findings underscore a strong correlation between the LSSE signal and the orientation of magnetic easy axis in compensated ferrimagnets and opens the possibility to tune LSSE through effective anisotropy.

The magnon propagation length (MPL) is one of the crucial factors to govern spin transport in a magnetic material. Here, we determine MPL ( $\xi$ ) in compensated ferrimagnetic Gd 3 Fe 5 O 12 (GdIG) thin films at room temperature by investigating longitudinal spin Seebeck effect (LSSE) in Gd 3 Ga 5 O 12 (GGG)/GdIG( $t$ )/Pt (5 nm) heterostructures with different thicknesses ( $t$ ) of the GdIG film. All films possess in-plane (IP) magnetic easy axis, and the compensation temperature shifts down to lower temperature with decreasing GdIG thickness. At room temperature, the LSSE signal is rather constant with thickness between $t = 221$ and 89 nm, but drops significantly below $t = 50$ nm. By fitting the thickness dependence of the LSSE voltage to a modified atomistic spin model considering the influence of saturation magnetization, we obtain $\xi $ = 45 nm ± 8 nm for GdIG thin films at room temperature. The MPL of GdIG is much shorter than that of Y 3 Fe 5 O 12 films ( $\xi $ ~90–140 nm), but higher than that of Fe 3 O 4 films ( $\xi $ ~20 nm). The obtained value of $\xi $ explains the drop in the LSSE voltage in GdIG films when the film thickness is reduced below 50 nm, knowledge of which is also essential to the design of spincaloritronic devices based on GdIG films.

Here, we explore the change in effective magnetic anisotropy of the ferrimagnetic (FM) insulator nickel ferrite (NFO) thin film due to the inclusion of monolayer graphene (MLG) grown on top of the NFO layer. This was done by performing radio frequency (RF) transverse susceptibility (TS) measurements on bare NFO and NFO/MLG bilayer samples for both in-plane (IP) and out-of-plane (OOP) configurations utilizing a tunnel diode oscillator technique. Our magnetometry measurements indicated an enhancement in the overall saturation magnetization of the NFO/MLG bilayer with respect to the bare NFO film. The TS measurements reveal that the inclusion of MLG reduces the effective magnetic anisotropy for both IP and OOP configurations drastically, by up to a factor of 2 over the temperature range 40 K ≤ T ≤ 280 K. Since NFO is a magnetic substrate, it is possible that NFO could induce magnetic ordering in MLG at the NFO/MLG interface via the magnetic proximity effect. Furthermore, since NFO is insulating and MLG is a semimetal, there likely exists a large conductivity difference at the interface, making charge transfer plausible. These two effects could modify the interfacial magnetism leading to a change in the effective magnetic anisotropy. These results highlight the importance of understanding the interfacial magnetism of FM/MLG heterostructures.

We report a comprehensive study of the temperature evolution of in-plane (IP) and out-of-plane (OOP) effective magnetic anisotropies in compensated ferrimagnetic ${\mathrm{Fe}}_{100\ensuremath{-}x}{\mathrm{Gd}}_{x}$ alloy films by employing direct current magnetometry and radiofrequency (RF) transverse susceptibility (TS) measurements. We suggest that our ${\mathrm{Fe}}_{100\ensuremath{-}x}{\mathrm{Gd}}_{x}$ system is chemically inhomogeneous and phase segregates into Fe- and Gd-enriched regions. Our IP and OOP magnetometry results indicate that the system undergoes a temperature-driven transformation from an IP-spin-configuration-dominated state to an OOP-spin-configuration-dominated state below a certain temperature (spin reorientation temperature). A two-step reversal behavior emerges in the OOP $M$($H$) loop near compensation, which we attribute to the sequential magnetization reversals of Fe- and Gd-enriched domains. Field-induced spin-flop transitions were also observed near the compensation. Our RF TS measurements indicate that the effective magnetic anisotropy for the OOP configuration dominates over that for the IP configuration below a certain spin reorientation temperature. Both IP and OOP anisotropy fields determined from our TS measurement exhibit a minimum around the compensation temperature, which has been explained in the framework of the Stoner-Wohlfarth model.