Ultrasmall Yttrium Iron Garnet Nanoparticles with High Coercivity at Low Temperature Synthesized by Laser Ablation and Fragmentation of Pressed Powders

Abstract

Pulsed laser ablation of pressed yttrium iron garnet powders in water is studied and compared to the ablation of a single-crystal target. We find that target porosity is a crucial factor, which has far-reaching implications on nanoparticle productivity. Although nanoparticle size distributions obtained by analytical disc centrifugation and transmission electron microscopy (TEM) are in agreement, X-ray diffraction and energy dispersive X-ray analysis show that only nanoparticles obtained from targets with densities close to that of a bulk target lead to comparable properties. Our findings also show why the gravimetrical measurement of nanoparticle productivity is often flawed and needs to be complemented by colloidal productivity measurements. The synthesized YIG nanoparticles are further reduced in size by laser fragmentation to obtain sizes smaller than 3 nm. Since the particle diameters are close to the YIG lattice constant, these ultrasmall nanoparticles reveal an immense change of the magnetic properties, exhibiting huge coercivity (0.11 T) and irreversibility fields (8 T) at low temperatures.

Laser Irradiation of Metal Oxide Films and Nanostructures: Applications and Advances

“…This process is applicable to most solid targets and produces stable and phase‐pure NPs with high dispersion. The LAL method has been utilized to produce NPs of several pure and doped metal oxides including CuO (Figure c), MnO x , Y 3 Fe 5 O 12 , Ag/TiO 2 , Y 2 O 3 :Eu 3+ , Gd 2 O 3 :Eu 3+ , Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce), Fe@Fe 2 O 3 or Fe 3 O 4 (Figure d), etc . Considering the wide applicability of LAL, a higher productivity of the process is essential for its industrial implementation.…”

“…The large temperature gradients and high diffusion rates during laser processing lead to epitaxial growth rates that are orders of magnitude larger and effective heating times much shorter than that for conventional thermal treatment . Furthermore, the laser irradiation technique has been utilized for processing of complex nanostructures, such as site‐specific growth of nanowires (NWs) (e.g., ZnO, TiO 2 ) and nanorods (NRs) (e.g., Fe 2 O 3 , Ag/ZnO), spatial patterning of nanocrystals (e.g., ZnO) and NWs (e.g., Al 2 O 3 ), fabrication of nanosheets (e.g., Fe 2 O 3 ) and clustered nanostructures (e.g., Ag–ZnS@ZnO, Ag/WO 3− x ), production of oxide nanoparticles (NPs) by laser ablation in liquid (e.g., CuO, MnO x , Y 3 Fe 5 O 12 , Ag/TiO 2 , Y 2 O 3 :Eu 3+ , Gd 2 O 3 :Eu 3+ , Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce), Fe@Fe 2 O 3 , or Fe 3 O 4 ), in situ formation of nanocomposites (e.g., Co 3 O 4 , MoO 2 , and Fe 3 O 4 particles embedded in graphene, ZnO particles embedded in poly(methyl methacrylate)), selective patterning of hybrid electrodes (e.g., Ni/NiO), direct scribing of fine structures (e.g., ITO), and direct writing of microdevices (e.g., TiO 2 , Cu/Cu 2 O).…”

Analysis of the Nanoparticle Dispersion and Its Effect on the Crystalline Microstructure in Carbon-Additivated PA12 Feedstock Material for Laser Powder Bed Fusion

“…36 mJ/cm 2 , 34 µJ/pulse, 0.094 mm 2 spot size) or with a 10 ps laser system operating at 532 nm and much higher fluence (Edgewave PX400-3-GH, Edgewave PX400-3-GH, Würselen, Germany, 80 kHz, 30 W 150 mJ/cm 2 , 375 µJ/pulse, 0.25 mm 2 spot size). A liquid jet set-up with a flow rate of 60 mL/min and a liquid jet diameter of 1.3 mm was utilized for laser postprocessing (LPP) [47,48]. At the given spot size and repetition rate of the laser system, this leads to multiple laser pulses per volume element [49].…”

Laser Fragmentation Synthesis of Colloidal Bismuth Ferrite Particles

“…Laser fragmentation of colloidal particles is an alternative method that is used to downsize oxide particles to diameters in the low single-nanometre range [13][14][15][16]. In contrast to other size reduction techniques, laser fragmentation is a wear-free method.…”