Chloridazon, a widely applied herbicide in European sugar beet farming, and its degradation products (desphenyl-chloridazon and methyl-desphenyl-chloridazon) are frequently found in surface waters, raising environmental and health concerns. Among the available treatment methods, adsorption stands out as an efficient and economical option, making the search for low-cost, high-performance sorbents essential. In this study, waste coffee grounds were converted into hierarchical porous carbon (HPC) with a specific surface area of about 900 m2 & sdot;g-1 and further activated using CO2 at 800 degrees C to yield an enhanced material (aHPC) with a surface area near 1100 m2 & sdot;g-1. Both adsorbents reached equilibrium within 20 minutes, with aHPC exhibiting notably higher uptake-448 mg & sdot;g-1 (chloridazon), 281 mg & sdot;g-1 (desphenyl-chloridazon), as well as 294 mg & sdot;g-1 (methyldesphenyl-chloridazon)-surpassing commercial activated carbon and other reported adsorbents. This outstanding performance is attributed to the hierarchical porous structure which at the same time allows for optimal water transport through the adsorbent and facilitates contact of the target molecules with the walls in the micro-and mesopores. Isotherm analysis favoured the Freundlich model, the kinetics followed a pseudo-second order law and thermodynamic measurements indicated the process to be exothermic in nature. X-ray photoelectron spectroscopy analysis identified hydrogen bonds and pi-pi interactions as driving forces for contaminant binding.

Composite materials based on nickel sulphide (Ni3S2) and selenide (Ni3Se2) with nanowire morphology were synthesised on Ni foam, modified by low-temperature hydrothermal treatment with or without Fe incorporation, and evaluated as electrocatalysts for the 5-hydroxymethylfurfural oxidation reaction (HMFOR) to 2,5-furandicarboxylic acid (FDCA), a key monomer for the production of bio-based plastics. The nickel selenide-based electrocatalysts outperformed their sulphide counterparts. Particularly, the selenide composite prepared by hydrothermal treatment at 40 °C without introducing Fe (H2O-Ni3Se2/Ni-foam-40) achieved nearly complete HMF conversion within 90 min at 1.6 V vs RHE (1.0 M KOH, room temperature), with 96 % yield and 94 % Faradaic efficiency towards FDCA. Under identical conditions, the benchmark Ni foam showed only 36 % HMF conversion and 7 % FDCA yield. Fe incorporation in the electrocatalyst was found to be detrimental for the HMFOR selectivity as it promoted the competing oxygen evolution reaction. In-situ Raman spectroscopy allowed identifying NiOOH as the key catalytic intermediate operating through an indirect mechanism in which HMF is oxidised by Ni(III) species that are continuously regenerated at the applied potential. The promising HMFOR performance shown by H2O-Ni3Se2/Ni-foam-40 was achieved with a much higher initial HMF concentration (100 mM) than generally used, bringing this electrochemical route closer to application.

Hydrogel adsorbents that possess both good mechanical strength and adsorption capabilities are crucial for practical wastewater treatment. However, achieving this balance has been demanding due to the trade-off between swelling properties and adsorption capacities in hydrogels. Although swelling increases the availability of functional groups and facilitates the diffusion of pollutants, it compromises the mechanical integrity. In this study, we address this challenge by developing double-network hydrogels based on poly(vinyl) alcohol and poly[2-(acryloyloxy)ethyl]trimethyl ammonium chloride, prepared via free-radical polymerization, and subsequent freeze-thaw treatment. These hydrogels were investigated for their efficacy in removing diclofenac sodium, a prevalent drug pollutant in pharmaceutical wastewater. By leveraging the synergistic effect of the physical and chemical networks, the prepared hydrogels exhibit intrinsic toughness and compressibility even in a fully swollen state. Most importantly, the maximum adsorption capacity yielded by the Langmuir model fitting was 1012 mg/g under natural conditions, they surpass all other hydrogel adsorbents proposed so far. Thermodynamic analysis implied the spontaneous and exothermic nature of diclofenac sodium adsorption process, while infrared and photoemission spectroscopy revealed that diclofenac sodium uptake is predominantly governed by ion exchange. Overall, double-network hydrogels offer considerable promise for eco-friendly and sustainable wastewater purification due to their high mechanical stability, outstanding adsorption performance, good reusability, and adaptability to diverse environmental conditions.

The effects of nitrosyl fluoride (FNO) gas treatment on the surface of GaN(0001) and its interface with sputtered Pt were investigated by hard x-ray photoelectron spectroscopy (HAXPES). Annealing GaN and Pt/GaN samples in an FNO gas atmosphere resulted in the appearance of prominent F 1s peaks in the HAXPES spectra, indicating the efficient formation of Ga–Fx bonding states not only in bare-GaN but also in Pt/GaN, even when the FNO gas treatment was performed after Pt deposition. In addition, the chemical shifts of the Ga 2p3/2 and N 1s peaks corresponded to a Fermi level shift toward the valence band. The FNO gas treatment induced greater oxidation of the GaN surface than the Pt/GaN interface. By contrast, at the Pt/GaN interface, the unintentionally formed oxide GaOx was reduced, resulting in an improvement of the electrical properties. The results of this study suggest that FNO gas treatment is an effective post-processing method for the fluorination of GaN-based systems after metal deposition.

Two-dimensional (2D) transition metal dichalcogenides have emerged as a promising platform for next-generation optoelectronic and spintronic devices. Mechanical exfoliation using adhesive tape remains the dominant method for preparing 2D materials of highest quality, including transition metal dichalcogenides, but always results in small-sized flakes. This limitation poses a significant challenge for investigations and applications where large scale flakes are needed. To overcome these constraints, we explored the preparation of 2D WS2 and WSe2 using a recently developed kinetic in situ single-layer synthesis method (KISS). In particular, we focused on the influence of different substrates, Au and Ag, and chalcogen atoms, S and Se, on the yield and quality of the 2D films. The crystallinity and spatial morphology of the 2D films were characterized using optical microscopy and atomic force microscopy, providing a comprehensive assessment of exfoliation quality. Low-energy electron diffraction verified that there is no preferential orientation between the 2D film and the substrate, while optical microscopy revealed that WSe2 consistently outperformed WS2 in producing large monolayers, regardless of the substrate used. Finally, X-ray diffraction and X-ray photoelectron spectroscopy demonstrate that no covalent bonds are formed between the 2D material and the underlying substrate. These results identify KISS method as a non-destructive method for a more scalable approach of high-quality 2D transition metal dichalcogenides.

In this contribution, we present the design of novel electrocatalysts for the oxygen evolution reaction (OER) consisting of nickel selenide nanowires decorated with iron-based species. The nickel-based nanowires were grown on Ni-foam through a selenidation process, followed by a hydrothermal treatment to introduce the Fe species (at 40, 80 or 120 degrees C). The resulting Fe-Ni3Se2/Ni-foam electrocatalysts exhibited high OER activity, with the material prepared at 40 degrees C (Fe-Ni3Se2/Ni-foam-40) showing the best performance by achieving 100 mA cm(-2) at an overpotential of only 250 mV. Comprehensive characterization using XRD, Raman spectroscopy, SEM, TEM, ICP-AES and XPS revealed that the enhanced activity of Fe-Ni3Se2/Ni-foam-40 arises from its favourable composite morphology, featuring a combination of mu m- and nm-sized structures, and from the effective incorporation of iron species, leading to a surface composition with a higher intrinsic OER activity. Importantly, Fe-Ni3Se2/Ni-foam-40 displayed excellent stability at an industrially-relevant current density of 500 mA cm(-2) during a prolonged chronopotentiometric test (100 h). Throughout this period, the morphology of the catalyst was largely preserved, despite a gradual surface transformation from metal selenides to (oxy)hydroxides. Furthermore, the overall water-splitting performance of Fe-Ni3Se2/Ni-foam-40 was validated in a commercial lab-scale (5 cm(2)) anion-exchange membrane (AEM) electrolyzer cell. These results demonstrate that Fe-Ni3Se2/Ni-foam-40 is an efficient and stable electrocatalyst, offering great promise for alkaline water electrolysis.

Hydrogen peroxide (H2O2) is recognized as an environmentally friendly oxidant with a wide range of applications, as well as a promising future energy carrier compared to hydrogen. Light driven and electrochemical production of H2O2 have gained significant interest as promising alternatives to the energy-intensive anthraquinone process. The two main approaches for the (photo)electrochemical production of H2O2 are the water oxidation reaction (WOR) and the oxygen reduction reaction (ORR). Considering the scarcity of noble metals, it is critical to develop successful high-performing electrocatalysts based on earth-abundant sources, thus adhering to principles of Green and Sustainable Chemistry. Herein, the use of the recently developed FeOx nanoparticles (NP) catalyst as a photocathode, circumventing catalyst deactivation and oxidation, is reported. The FeOx NP photocathode exhibited an increased catalytic current by 41% under illumination, demonstrating the advantage of a photoelectrochemical (PEC) setup. Combining the FeOx NP photocathode for ORR with a Ti-doped α-Fe2O3 photoanode for WOR, robust PEC performance is successfully achieved in bias-free conditions. The structural integrity of the FeOx NP photocathode is preserved without degradation or oxidation for extended periods of irradiation of up to 10 h testimony of a benign and robust process.

We successfully demonstrate the synthesis of alanine from glycerol and NH3 without additional H2, using a novel Ru-catalyst with optimized metal-support interactions. Three heterogeneous catalysts (Ru/TiO2-Anatase, Ru/ TiO2-Rutile, and Ru/TiO2-P25) were compared, with Ru/TiO2-Rutile showing superior performance, giving complete glycerol conversion with 37 % alanine and 26 % lactate yield after 6 h at 220 degrees C. This performance matches that of state-of-the-art catalysts, but with lower Ru loading (leading to an approximately three-fold higher turnover number) and without external H2 supply. Catalyst characterization revealed that the metal- support interactions in Ru/TiO2-Rutile lead to smaller, well-dispersed Ru nanoparticles (d = 2.3 nm) and lower degree of overlayer TiO2-x formation compared to Ru/TiO2-Anatase, which together contribute to higher Ru accessibility (ARu = 22 %) and thus higher number of active sites per unit mass of Ru, despite the lower surface area of rutile. The reusability of Ru/TiO2-Rutile is strongly influenced by the amount of NaOH utilized in the reaction, with a low NaOH: glycerol ratio (1.1) allowing to recycle the catalyst while largely preserving its activity.

Defect engineering of semiconductors is a promising approach for enhancing their photocatalytic activity for organic pollutant degradation in water. In this study, we present an effective strategy to tune the type, location, and number of defects in nanostructured zinc oxide (ZnO) by controlling the atmosphere in which the material was prepared (from high to virtually no exposure to O2). By decreasing O2 exposure during the synthesis, ZnO displayed an increasing number of surface and near-surface O vacancies (as determined by x-ray photoelectron spectroscopy and photoluminescence) and fewer bulk defects (as indicated by electron paramagnetic resonance spectroscopy). This approach allowed establishing the role that these defects exert on the photocatalytic activity of ZnO in removing pollutants from water. The optimum photocatalytic activity was achieved with ZnO nanoparticles that are rich in surface O vacancies but poor in bulk Zn and O vacancies. This ZnO photocatalyst outperformed P25-TiO2 in the degradation of phenol, both under ultraviolet (UV) (73% vs. 56% removal) and visible irradiation (15% vs. 6% removal). Furthermore, it maintained its activity upon reuse and proved versatile in the degradation of several types of pollutants (bisphenol A, rhodamine B, imidacloprid, and ibuprofen sodium), highlighting its potential for practical water treatment applications.

To enable green hydrogen production through alkaline water electrolysis, it is crucial to enhance the activity of nickel electrocatalysts towards the oxygen evolution reaction (OER), while preserving high stability. Here, we present a new and effective strategy to achieve this target through the introduction of short, periodical regeneration steps, complemented with the accurate tuning of traces of iron in the electrolyte. This strategy allowed retaining the enhanced activity brought about by the iron species adsorbed on the nickel electrode for the whole test duration (72 h) at an industrially relevant current density of 300 mA cm-2 with a 1.0 M KOH electrolyte containing ca. 100 ppb of iron (mimicking a commercial electrolyte). Under the same conditions but without regeneration, a dramatic deactivation was observed after ca. 18 h. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) highlighted that such deactivation is correlated to the loss of iron species from the surface of the electrode. The regeneration steps help retain the iron species on the surface of the nickel electrode, thus granting the desired high OER activity and stability. We estimated that this regeneration strategy could lead to up to 18% energy saving compared to the current standard operating conditions of alkaline electrolysers.

The effects of NF3 or F2 gas annealing on epitaxially grown GaN and its interface with sputter-deposited Pt were investigated using hard X-ray photoelectron spectroscopy. Annealing GaN and Pt/GaN samples in an NF3 atmosphere led to the emergence of prominent F 1s peaks and chemically shifted Ga 2p peaks, indicating the efficient formation of Ga–F x species not only in the bare GaN surface but also in the Pt/GaN interface, even when the NF3 treatment was performed after the Pt was deposited. By contrast, F2 annealing also led to the fluorination of the GaN surface and nonfluorination of the Pt/GaN interface. Although the plasma sputtering process removed F from the surface, band shifts were observed when the treatment conditions were varied. The findings in this study suggest that NF3 treatment is an effective post-processing method for fluorinating GaN-based systems before or after metal deposition.

In this work, we investigated the inherent electrocatalytic activity of nickel borides in an important reaction in the context of electrochemical valorization of biomass as the oxidation of hydroxymethylfurfural (5-HMF) to furan dicarboxylic acid (FDCA). For this purpose, nickel borides (NixB, x = 2 and 3) in the form of phase-pure nanocrystals (NCs) were synthesized through a solid-state synthesis method, supported on carbon paper and then tested as electrocatalysts for the oxidation of hydroxymethylfurfural (pH 12.9 or 13.9, 1.8 V vs. RHE, 3 h) by comparing their activity to that of Ni nanocrystals of similar average particle size (36-39 nm). Ni3B NCs achieved the highest 5-HMF conversion and Faradaic efficiency towards 5-HMF oxidation (Conv.5-HMF = 70%, FE = 94%), which is a markedly better performance compared to Ni2B NCs (Conv.5-HMF = 57%, FE = 72%) and to Ni nanoparticles (Conv.5-HMF = 58%, FE = 65%), thus unequivocally demonstrating for the first time the superior activity brought about by Ni3B. Based on a combination of physicochemical and electrochemical characterization (XPS, SEM, TEM, Cdl analysis), the better performance of the Ni3B-based electrocatalyst is attributed to differences in surface composition compared to the Ni2B-based electrocatalyst and to differences in terms of electrochemical surface area and/or bulk chemical features compared to the Ni-based electrocatalyst. Notably, these results were achieved with a remarkably low electrocatalyst loading (0.05 mg cm-2), leading to significantly higher turnover frequency compared to state-of-the-art nickel boride electrocatalysts for this reaction. A kinetic study showed that NixB NCs catalyze the electrosynthesis of FDCA from 5-HMF both through a direct and indirect mechanism, with the contribution of each changing as a function of the pH of the electrolyte.

Solid polymer electrolytes (SPEs) offer inherent advantages for battery applications, such as high safety and excellent processability, but their practical use is limited by challenges like low ionic conductivity, subpar mechanical properties, and instability of the electrode/electrolyte interface. Here, novel SPEs are developed by embedding 2D MXenes decorated at the surface with methoxypolyethylene glycol chains into poly(vinylidene fluoride)-hexafluoropropylene matrices, enhanced with succinonitrile as a plasticizer. This innovative design improves the compatibility of the modified MXene in poly(vinylidene fluoride)-hexafluoropropylene and, together with the synergistic effects of succinonitrile, promotes the dissociation of lithium salt. The SPE achieves ionic conductivity of 1.49 x 10-4 S cm-1 at 30 degrees C, and a Li-ion transference number of 0.59. These results are supported by comprehensive experimental characterization, COMSOL simulations, and DFT calculations. This SPE enables stable and reversible Li plating/stripping for over 2100 h in Li/Li symmetric cells, while fabricated Li/LiFePO4 full cells deliver a notable capacity of 135.4 mAh g-1 with an average Coulombic efficiency of 98.9% after 100 cycles at 0.2 C. Furthermore, the Li/LiNi0.6Co0.2Mn0.2O2 full cells also demonstrate a capacity of 140.5 mAh g-1 after over 200 cycles at 0.5 C, showcasing an impressive capacity retention rate of 99.6%.

A novel oxygen evolution reaction (OER) electrocatalyst was prepared by a synthesis strategy consisting of the solvothermal growth of Ni3S2 nanostructures on Ni foam, followed by hydrothermal incorporation of Fe species (Fe-Ni3S2/Ni foam). This electrocatalyst displayed a low OER overpotential of 230 mV at 100 mAcm(-2), a low Tafel slope of 43 mVdec(-1), and constant performance at an industrially relevant current density (500 mAcm(-2)) over 100 h in a 1.0 M KOH electrolyte, despite a minor loss of Fe in the process. Based on a detailed characterization by (in situ) Raman spectroscopy, (quasi-in situ) XPS, SEM, TEM, XRD, ICP-AES, EIS, and C-dl analysis, the high OER activity and stability of Fe-Ni3S2/Ni foam were attributed to the nanostructuring of the surface in the form of stable nanosheets and to the combination of Ni3S2 granting suitable electrical conductivity with newly formed NiFe-based (oxy)hydroxides at the surface of the material providing the active sites for OER.

Hydrogen peroxide (H2O2) is a valuable green oxidant with a wide range of applications. Furthermore, it is recognized as a possible future energy carrier achieving safe operation, storage and transportation. The photochemical production of H2O2 serves as a promising alternative to the waste- and energy-intensive anthraquinone process. Following the 12 principles of Green Chemistry, we demonstrate a facile and general approach to sustainable catalyst development utilizing earth-abundant iron and biobased sources only. We developed several iron oxide (FeOx) nanoparticles (NPs) for successful photochemical oxygen reduction to H2O2 under visible light illumination (445 nm). Achieving a selectivity for H2O2 of >99%, the catalyst material could be recycled for up to four consecutive rounds. An apparent quantum yield (AQY) of 0.11% was achieved for the photochemical oxygen reduction to H2O2 with visible light (445 nm) at ambient temperatures and pressures (9.4–14.8 mmol g−1 L−1). Reaching productivities of H2O2 of at least 1.7 ± 0.3 mmol g−1 L−1 h−1, production of H2O2 was further possible via sunlight irradiation and in seawater. Finally, a detailed mechanism has been proposed on the basis of experimental investigation of the catalyst's properties and computational results.

Metal borides, a class of materials intensively used in industry as superconductors, magnetic materials, or hot cathodes, remain largely unexplored at the nanoscale mainly due to the difficulty in synthesizing single-phase nanocrystals. Recent works have shown that synthetic methods at lower temperatures (<400 degrees C) yield amorphous polydisperse nanoparticles, while phase purity is an issue at higher temperatures. Among all the metal-rich borides, nickel borides (Ni x B) could be a potential catalyst for a broad range of applications (hydrogenations, electrochemical hydrogen, and oxygen evolution reactions) under challenging conditions (such as high pH or high temperatures). Here, we report a novel solid-state method to synthesize Ni x B nanopowders (with a diameter of approximately 45 nm) and their conversion into colloidal suspensions (inks) through treatment of the nanocrystal surface. For the solid-state synthesis, we used commercially available salts and explored the reaction between the Ni and B sources while varying the synthetic parameters under mild and solvent-free reaction conditions. We show that pure phase Ni3B and Ni2B NCs can be obtained with high yield in the pure phase using as precursors NiCl2 and Ni, respectively. Through extensive mechanistic studies, we show that Ni nanoclusters (1-2 nm) are an intermediate in the boriding process, while the metal co-reactant lowers the decomposition temperature of NaBH4 (used as a reducing agent and B source). Size control can instead be exerted through reaction mediators, as seen from the differential nucleation and growth of Ni (clusters) or Ni x B NCs when employing L- (amine, phosphine) and X-type (carboxylate) mediators. Applying surface engineering methods to our Ni x B NCs, we stabilized them with inorganic (NOBF4) or organic (borane tert-butyl amine, oleylamine) ligands in the appropriate solvent (DMSO, hexane). With this method, we produce stable inks for further solution processing applications. Our results provide tools for further development of catalysts based on Ni x B NCs and pave the way for synthesizing other metal boride colloidal nanostructures.

Metal borides, a class of materials intensively used in industry as superconductors, magnetic materials, or hot cathodes, remain largely unexplored at the nanoscale mainly due to the difficulty in synthesizing single-phase nanocrystals. Recent works have shown that synthetic methods at lower temperatures (<400 degrees C) yield amorphous polydisperse nanoparticles, while phase purity is an issue at higher temperatures. Among all the metal-rich borides, nickel borides (NixB) could be a potential catalyst for a broad range of applications (hydrogenations, electrochemical hydrogen, and oxygen evolution reactions) under challenging conditions (such as high pH or high temperatures). Here, we report a novel solid-state method to synthesize NixB nanopowders (with a diameter of approximately 45 nm) and their conversion into colloidal suspensions (inks) through treatment of the nanocrystal surface. For the solid-state synthesis, we used commercially available salts and explored the reaction between the Ni and B sources while varying the synthetic parameters under mild and solvent-free reaction conditions. We show that pure phase Ni3B and Ni2B NCs can be obtained with high yield in the pure phase using as precursors NiCl2 and Ni, respectively. Through extensive mechanistic studies, we show that Ni nanoclusters (1-2 nm) are an intermediate in the boriding process, while the metal co-reactant lowers the decomposition temperature of NaBH4 (used as a reducing agent and B source). Size control can instead be exerted through reaction mediators, as seen from the differential nucleation and growth of Ni (clusters) or NixB NCs when employing L-(amine, phosphine) and X-type (carboxylate) mediators. Applying surface engineering methods to our NixB NCs, we stabilized them with inorganic (NOBF4) or organic (borane tert-butyl amine, oleylamine) ligands in the appropriate solvent (DMSO, hexane). With this method, we produce stable inks for further solution processing applications. Our results provide tools for further development of catalysts based on NixB NCs and pave the way for synthesizing other metal boride colloidal nanostructures.

Poly(3,4‐ethylenedioxy thiophene):poly(styrenesulfonate) (PEDOT:PSS) exhibits valuable characteristics concerning stability, green‐processing, flexibility, high electrical conductivity, and ease of property modulation, qualifying it as one of the most promising p‐type organic conductors for thermoelectric (TE) applications. While blending with inorganic counterparts is considered a good strategy to further improve polymeric TE properties, only a few attempts succeed so far due to inhomogeneous embedding and the non‐ideal organic‐inorganic contact. Here a new strategy to include nanoparticles (NPs) without any ligand termination inside PEDOT:PSS thin films is proposed. Spark discharge‐generated tin oxide NPs (SnOx‐NPs) are “gently” and homogenously deposited through low‐energy diffusion mode. Strong interaction between naked SnOx‐NPs and PSS chains occurs in the topmost layer, causing a structural reorganization towards an improved PEDOT chains crystalline packing at the bottom, providing a positive contribution to the electrical conductivity. Meanwhile, dedoping and energy filtering effect introduced by the SnOx‐NPs cause dramatic Seebeck coefficient enhancement. The optimized power factor of 116 μWm−1 K−2 achieved is more than six times higher than the value found for the film without NPs. This easy and efficient strategy promises well for future mass production of flexible TE devices and the mechanism revealed may inspire future research on TEs and flexible electronics.

This study describes the potential and challenges involved with the use of wide bandgap kesterite absorbers in tandem solar cells.

Orthorhombic rare-earth trivalent manganites RMnO3 (R = Er-Lu) were self-doped with Mn to form (R0.667Mn0.333)MnO3 compositions, which were synthesized by a high-pressure, high-temperature method at 6 GPa and about 1670 K from R2O3 and Mn2O3. The average oxidation state of Mn is 3+ in (R0.667Mn0.333)MnO3. However, Mn enters the A site in the oxidation state of 2+, creating the average oxidation state of 3.333+ at the B site. The presence of Mn2+ was confirmed by hard X-ray photoelectron spectroscopy measurements. Crystal structures were studied by synchrotron powder X-ray diffraction. (R0.667Mn0.333)MnO3 crystallizes in space group Pnma with a = 5.50348(2) Å, b = 7.37564(1) Å, and c = 5.18686(1) Å for (Lu0.667Mn0.333)MnO3 at 293 K, and they are isostructural with the parent RMnO3 manganites. Compared with RMnO3, (R0.667Mn0.333)MnO3 exhibits enhanced Néel temperatures of about TN1 = 106-110 K and ferrimagnetic or canted antiferromagnetic properties. Compounds with R = Er and Tm show additional magnetic transitions at about TN2 = 9-16 K. (Tm0.667Mn0.333)MnO3 exhibits a magnetization reversal or negative magnetization effect with a compensation temperature of about 16 K.