Magnetoresistive La_0.67Sr_0.33MnO₃ Nanowires

Abstract

The reactants used in this preparation, SnCl 4´5 H 2 O and propylene oxide, were obtained from Aldrich. In a typical synthesis, SnCl 4´5 H 2 O (0.56 g, 1.6 mmol) was dissolved in 2.5 mL of water, followed by the addition of propylene oxide (1.02 g, 17 mmol) to the clear solution. The reaction mixture was stirred for 2 min, transferred to a plastic mold, and the solution was allowed to gel at room temperature for 24 h. Gel formation typically occurred within~10 min, affording a translucent monolith. The monolithic gel was then soaked in a bath of absolute ethanol for 1 day to exchange the water and reaction byproducts from the pores of the material. The wet, tin oxide gel was processed in a Polaron critical-point extractor. The ethanol in the pores of the wet gel was exchanged with liquid CO 2 for 3±4 days, after which time, the temperature was ramped up to~45 C, while maintaining a pressure of~100 bar (10 7 Pa). The autoclave was then depressurized at a rate of~7 bar h ±1 , affording the material as a right-circular cylinder (volume~2.2 cm 3 ) with typical densities of 0.20±0.25 g cm ±3 (~97 % porous solids). The bulk density of the aerogel was determined by measuring the dimensions and mass of the monolithic sample. HRTEM was performed using a Philips CM300FEG electron microscope operating at 300 keV. Powder XRD data were collected using an APD3720 PEI diffractometer with a Cu Ka radiation source. Surface-area determination and pore volume and size analysis were performed by BET and BJH methods using an ASAP 2000 Surface Area Analyzer (Micromeritics Instrument Corporation). XANES experiments were performed at undulator beamline 8.0 at the Advanced Light Source, Lawrence Berkeley National Laboratory [20]. Spectra were obtained by recording the total electron yield (TEY), probing the material properties averaged over the first~10±20 nm from the sample surface [14]. After a linear background subtraction, all XANES spectra were normalized to the postedge step heights. The monochromator was calibrated by aligning the first intense peak of the O K-edge XANES spectrum of the SnO 2 reference powder to 544.0 eV.

Large low field magnetoresistance in La0.67Sr0.33MnO3 nanowire devices

“…Due to the difficulty in LSMO nanowire growth, the electrical and magnetotransport studies on one-dimensional LSMO nanowires are not completely explored [9][10][11] and no work has been reported yet on LFMR at room temperature in LSMO nanowires. 12,13 In this work, we have carried out a systematic investigation on magnetotransport properties of electrospun LSMO wires with diameters ranging from 80 to 300 nm. The nanowires with diameters around 100 nm exhibit large LFMR effect at room temperature.…”

Single‐Crystalline La0.7Sr0.3MnO3 Nanowires by Polymer‐Template‐Directed Chemical Solution Synthesis

“…[9][10][11][12] Driven by their potential applications in diverse areas including bolometric applications, [13] magnetic recording, spintronic devices, [14] flash memory electroresistive devices, [15] and biomedical applications [16] considerable research has been devoted to the synthesis and characterization of manganites in both bulk and thin film forms. In the last years, a strong interest has been raised on manganite-based nanostructures such as 1D nanowires and nanotubes [17][18][19][20] and 0D nanocubes and nanoparticles [16,[21][22] have been reported. The delicate balance that exists between electronic, magnetic, and lattice degrees of freedom can be unbalanced in these materials at the nanoscale, [23] and thus new outstanding properties can be achieved.…”

Spin Nematicity and Large Low‐Field Positive Magnetoresistance in a Half‐Doped Manganite: An Approach Exploiting Cation Size Disorder

“…Low fi eld MR response for our LCSY sample with σ 2 = 0.001 Å 2 (see also Figure 4 d,e), and for several other MR materials reported in literatures. [43][44][45][46][47][48][49][50] Note that the present PMR is reversed to identical negative values (−MR+) for comparison convenience. , a spontaneous A type-like AFM arrangement is assumed for the nematic fi laments, and its zero fi eld electron itinerancy is determined by the allowed spin polarized transport along the fi laments, as indicated by a green signal with an upward green arrow in e).…”

“…The water-green matrix denotes the AFM-COO host which owns alternating e g orbital (in yellow) ordered [ of MR in its faster low fi eld response, higher operating temperature, as well as a much higher PMR magnitude up to 40% at 1 kOe. Although the present low fi eld MR exhibiting below T N ≈ 150 K is far from optimal, it importantly suggests that the low fi eld spin polarized transport can be improved not only by grain boundary modifi cation or nanofabrication in FM materials, [ 43,44,47 ] but also effi ciently in AFM-COO system through intragrain tailoring of the spin nematic states.…”

“…Over the past decades, driven by the limitation of CMR with Tesla magnetic fi eld, much efforts have been made to improve the MR response in perovskite manganites, such as (La,Sr)MnO 3 , [43][44][45] and also to search more sensitive MR in other systems such as Tl 1.7 Sc 0.3 Mn 2 O 7 , [ 46 ] CrO 2 , [ 47 ] CaCu 3 Mn 4 O 12 , [ 48 ] and Sr 2 FeMoO 6 . [ 49,50 ] These work enrich our understanding of the low fi eld magnetotransport, however, a challenge remains on achieving low fi eld MR of the best performance.…”