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Polycrystalline GdFe1âˆ' x Ni x O3 (x  = 0.00, 0.02, 0.04) samples was synthesised using a glycine assisted solâ€"gel method to investigate the enhanced magnetic and electric properties of Ni substituted GdFeO3 systems. TG-DSC analysis of prepared samples confirms that GdFe1âˆ' x Ni x O3 have good thermal stability in high temperatures. The system has been stabilized in an orthorhombic structure with space group Pbnm. The elemental composition of GdFe1âˆ' x Ni x O3 has been estimated from EDAX spectrum. The results showed oxygen deficiency on increasing the Ni substitution and it has been supported by Rietveld refinement. FE-SEM images and Brunauerâ€"Emmettâ€"Teller analysis reveals that GdFe1âˆ' x Ni x O3 is a highly porous material and its porosity and specific area increases with Ni substitution. Magnetic measurements indicates that the system exhibited ferrimagnetic behaviour at low temperatures and canted antiferromagnetic behaviour at room temperature. For x  = 0.04 Ni content, magnetization reversal for applied field of 25 Oe has been observed. Increased coercivity of GdFeO3 with Ni substitution has been attributed to the grain size effect. From electrical point of view, dielectric permittivity of GdFeO3 has been enhanced with Ni substitution. This enhancement has been attributed to the cumulative effects of hopping of Fe2+â€"Fe3+ ions, grainâ€"grain boundary contribution, and space charge polarization. The role of grainâ€"grain boundary contribution is evident from electric modulus spectrum. The space charge effect has been realized in both impedance spectrum and dielectric loss. Temperature-dependent dielectric studies were conducted to understand the mechanisms and various aspects that contribute to the dielectric enhancement. A highly lossy capacitive nature in the P â€" E loop also suggests space charge effects due to Ni substitution in Fe sites. Availability of free charge carrier concentration is correlated with the optical properties of GdFe1âˆ' x Ni x O3. The decrease of optical band gap (2.5â€"2.21 eV) on increasing Ni content suggests the increasing electronic contribution in the system. [ABSTRACT FROM AUTHOR]

The exchange bias phenomenon, inherent in exchange-coupled ferromagnetic and antiferromagnetic systems, has intrigued researchers for decades. Van der Waals materials, with their layered structures, offer an ideal platform for exploring exchange bias. However, effectively manipulating exchange bias in van der Waals heterostructures remains challenging. This study investigates the origin of exchange bias in MnPS 3 /Fe 3 GeTe 2 van der Waals heterostructures, demonstrating a method to modulate nearly 1000% variation in magnitude through simple thermal cycling. Despite the compensated interfacial spin configuration of MnPS 3 , a substantial 170 mT exchange bias is observed at 5 K, one of the largest observed in van der Waals heterostructures. This significant exchange bias is linked to anomalous weak ferromagnetic ordering in MnPS 3 below 40 K. The tunability of exchange bias during thermal cycling is attributed to the amorphization and changes in the van der Waals gap during field cooling. The findings highlight a robust and adjustable exchange bias in van der Waals heterostructures, presenting a straightforward method to enhance other interface-related spintronic phenomena for practical applications. Detailed interface analysis reveals atom migration between layers, forming amorphous regions on either side of the van der Waals gap, emphasizing the importance of precise interface characterization in these heterostructures., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

Two-dimensional van der Waals (vdW) heterostructures are an attractive platform for studying exchange bias due to their defect-free and atomically flat interfaces. Chromium thiophosphate (CrPS 4 ), an antiferromagnetic material, possesses uncompensated magnetic spins in a single layer, rendering it a promising candidate for exploring exchange bias phenomena. Recent findings have highlighted that naturally oxidized vdW ferromagnetic Fe 3 GeTe 2 exhibits exchange bias, attributed to the antiferromagnetic coupling of its ultrathin surface oxide layer (O-FGT) with the underlying unoxidized Fe 3 GeTe 2 . Anomalous Hall measurements are employed to scrutinize the exchange bias within the CrPS 4 /(O-FGT)/Fe 3 GeTe 2 heterostructure. This analysis takes into account the contributions from both the perfectly uncompensated interfacial CrPS 4 layer and the interfacial oxide layer. Intriguingly, a distinct and nonmonotonic exchange bias trend is observed as a function of temperature below 140 K. The occurrence of exchange bias induced by a "preset field" implies that the prevailing phase in the polycrystalline surface oxide is ferrimagnetic Fe 3 O 4 . Moreover, the exchange bias induced by the ferrimagnetic Fe 3 O 4 is significantly modulated by the presence of the van der Waals antiferromagnetic CrPS 4 layer, forming a heterostructure, along with additional iron oxide phases within the oxide layer. These findings underscore the intricate and complex nature of exchange bias in van der Waals heterostructures, highlighting their potential for tailored manipulation and control.

Polycrystalline GdFe 1- x Ni x O 3 ( x  = 0.00, 0.02, 0.04) samples was synthesised using a glycine assisted sol-gel method to investigate the enhanced magnetic and electric properties of Ni substituted GdFeO 3 systems. TG-DSC analysis of prepared samples confirms that GdFe 1- x Ni x O 3 have good thermal stability in high temperatures. The system has been stabilized in an orthorhombic structure with space group Pbnm . The elemental composition of GdFe 1- x Ni x O 3 has been estimated from EDAX spectrum. The results showed oxygen deficiency on increasing the Ni substitution and it has been supported by Rietveld refinement. FE-SEM images and Brunauer-Emmett-Teller analysis reveals that GdFe 1- x Ni x O 3 is a highly porous material and its porosity and specific area increases with Ni substitution. Magnetic measurements indicates that the system exhibited ferrimagnetic behaviour at low temperatures and canted antiferromagnetic behaviour at room temperature. For x  = 0.04 Ni content, magnetization reversal for applied field of 25 Oe has been observed. Increased coercivity of GdFeO 3 with Ni substitution has been attributed to the grain size effect. From electrical point of view, dielectric permittivity of GdFeO 3 has been enhanced with Ni substitution. This enhancement has been attributed to the cumulative effects of hopping of Fe 2+ -Fe 3+ ions, grain-grain boundary contribution, and space charge polarization. The role of grain-grain boundary contribution is evident from electric modulus spectrum. The space charge effect has been realized in both impedance spectrum and dielectric loss. Temperature-dependent dielectric studies were conducted to understand the mechanisms and various aspects that contribute to the dielectric enhancement. A highly lossy capacitive nature in the P - E loop also suggests space charge effects due to Ni substitution in Fe sites. Availability of free charge carrier concentration is correlated with the optical properties of GdFe 1- x Ni x O 3 . The decrease of optical band gap (2.5-2.21 eV) on increasing Ni content suggests the increasing electronic contribution in the system., (© 2021 IOP Publishing Ltd.)