Stacked Nanosheets of Pr_1–xCa_xMnO₃ (x = 0.3 and 0.49): A Ferromagnetic Two-Dimensional Material with Spontaneous Exchange Bias

Abstract

planar architectures of inorganic materials have attracted great attention owing to their fascinating physical properties. However, nanosheets of the technologically relevant doped rare-earth manganites are still elusive. Stacked 10−14 nm thick nanosheets of phase pure Pr 1−x Ca x MnO 3 (PCMO; x = 0.3 and 0.49) were obtained by decomposition of carbon coated CaCO 3 /MnCO 3 microsheets and Pr 2 O 2 CO 3 aggregates, the latter synthesized under pressure at 500−800 °C. The PCMO nanosheets had flatter Mn−O−Mn tilt angles in the MnO 6 octahedra and ferromagnetic (FM) moments at 5 K. Spontaneous exchange bias (SEB) coupling between the antiferromagnetic (AF)/FM spins was observed at 5 K under zero-field cooling. High FM moments and SEB were possible due to the long-range magnetic interactions in the stacked 2D arrangement of Mn 3+ /Mn 4+ d-electron spins, where charge ordering was completely suppressed. The SEB behavior was dependent on the initial magnetization process and the direction of rotation of the random spins at the AF/FM interface.

Efficient Dye Degradation Catalyzed by Manganese Oxide Nanoparticles and the Role of Cation Valence

“…e g orbital vacancy as in Mn 4+ results in too little interaction with the adsorbate which explains the least performing δ‐MnO 2 NPs where promotion of electron transfer to form the radicals required for MB degradation is slowed down. Unlike the present study, the maximum filling of the e g orbitals is always not beneficial for practical applications, for example trivalency of cations in metal oxides is useful for oxygen evolution reactions, and partial conversion of Mn 3+ to Mn 4+ ions facilitates ferromagnetic double exchange in rare‐earth doped manganites …”

“…Unlike the present study, the maximum filling of the e g orbitals is always not beneficial for practical applications, for example trivalency of cations in metal oxides is useful for oxygen evolution reactions, [44] and partial conversion of Mn 3 + to Mn 4 + ions facilitates ferromagnetic double exchange in rareearth doped manganites. [45][46][47] Thus the benefits of optimal e g orbital filling are limited to the reactions involving transfer of electrons for generation of radicals, and can be generalized for other Fenton catalysts used in the degradation of several organic dyes present in wastewater.…”

Positive to negative zero-field cooled exchange bias in La0.5Sr0.5Mn0.8Co0.2O3 ceramics

“…Usually in the negative FC and ZFC-EB effects, the absolute value of H EB ( H EB < 0) approximately linearly decreases with increasing temperature and gradually disappears around the blocking temperature T B , which can be attributed to the decrease of the AFM anisotropy paralleling to the direction of positive magnetic field with the increase of temperature 13 16 17 18 19 20 21 29 . However, if there is AFM bidomain in the initial state, the decrease of the anisotropy of the right AFM domain would decrease the needed to generate the rotation of the interfacial AFM spins from negative to positive direction.…”

“…From then on, the ZFC-EB effect has been observed in different systems, such as Mn 2 PtGa alloy 14 , BiFeO 3 –Bi 2 Fe 4 O 9 nanocomposite 15 , YMnO 3 nanoparticles 16 , Ni 2 Mn 1.4 Ga 0.6 alloy 17 , La 1.5 Sr 0.5 CoMnO 6 polycrystalline ceramics 18 , Pr 1− x Ca x MnO 3 nanosheet 19 , Ni 50 Mn 36 Co 4 Sn 10 alloy 20 , antiperovskite compound PdNCr 3 21 , Co 0.8 Cu 0.2 Cr 2 O 4 22 and Y 0.9 Pr 0.1 CrO 3 ceramics 23 . In most cases, the appearance of such ZFC-EB effect is related to newly established interface with AFM unidirectional anisotropy, and the formation or growth of FM (or superferromagnet, SFM) domains at the expense of pinning subsystem (AFM matrix or spin glass) has been proposed as a possible way 13 16 17 18 19 20 21 . However, almost all these studies show only the negative ZFC-EB effect, in another word, shift of the hysteresis loop in the opposite direction to the initial magnetization field.…”

The destructive spontaneous ingression of tunable silica nanosheets through cancer cell membranes

“…The impetus received from graphene research has catapulted interest in two-dimensional (2D) inorganic graphene analogues primarily through the resurgence of materials such as MXenes1 and transition metal dichalcogenides2 among others 3–5. A parallel effort has emerged to discern the biological and environmental applications of these 2D materials,6 for example, the antibacterial activity of MXenes,7 and bio-sensing properties of MoS 2 8.…”