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Title: Strain development during the phase transition of La(Fe,Mn,Si){sub 13}H{sub z}

Abstract

We use powder X-ray diffraction to evaluate the temperature dependence of the crystalline properties during the magnetic phase transition of La(Fe,Mn,Si){sub 13}H{sub z} as a function of the Fe/Mn/Si ratio. Both the paramagnetic and ferromagnetic phases were observed as peak overlaps in the patterns around the Curie temperature (T{sub C}) occurring continuously in a temperature range of about 5 K around T{sub C.} Using the Williamson-Hall method, we evaluate the strain developing in the crystallites during the transition and find that it is associated with the growth of the paramagnetic phase as the transition occurs. Based on our measurements and microstructure analyses, we propose that cracking during the phase transition is due to or aggravated by the small content of a La-rich phase.

Authors:
; ; ; ;  [1];  [2]
  1. Department of Energy Conversion and Storage, Technical University of Denmark, Frederiksborgvej 399, DK-4000 Roskilde (Denmark)
  2. Department of Chemistry, Technical University of Denmark, Anker Engelunds Vej, DK-2800 Lyngby (Denmark)
Publication Date:
OSTI Identifier:
22594393
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 5; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CRACKING; CURIE POINT; IRON; LANTHANUM COMPOUNDS; MANGANESE; MICROSTRUCTURE; PARAMAGNETISM; PEAKS; PHASE TRANSFORMATIONS; POWDERS; SILICON; STRAINS; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE; X RADIATION; X-RAY DIFFRACTION

Citation Formats

Neves Bez, Henrique, E-mail: hnbe@dtu.dk, Nielsen, Kaspar K., Smith, Anders, Norby, Poul, Bahl, Christian R. H., and Ståhl, Kenny. Strain development during the phase transition of La(Fe,Mn,Si){sub 13}H{sub z}. United States: N. p., 2016. Web. doi:10.1063/1.4960358.
Neves Bez, Henrique, E-mail: hnbe@dtu.dk, Nielsen, Kaspar K., Smith, Anders, Norby, Poul, Bahl, Christian R. H., & Ståhl, Kenny. Strain development during the phase transition of La(Fe,Mn,Si){sub 13}H{sub z}. United States. doi:10.1063/1.4960358.
Neves Bez, Henrique, E-mail: hnbe@dtu.dk, Nielsen, Kaspar K., Smith, Anders, Norby, Poul, Bahl, Christian R. H., and Ståhl, Kenny. Mon . "Strain development during the phase transition of La(Fe,Mn,Si){sub 13}H{sub z}". United States. doi:10.1063/1.4960358.
@article{osti_22594393,
title = {Strain development during the phase transition of La(Fe,Mn,Si){sub 13}H{sub z}},
author = {Neves Bez, Henrique, E-mail: hnbe@dtu.dk and Nielsen, Kaspar K. and Smith, Anders and Norby, Poul and Bahl, Christian R. H. and Ståhl, Kenny},
abstractNote = {We use powder X-ray diffraction to evaluate the temperature dependence of the crystalline properties during the magnetic phase transition of La(Fe,Mn,Si){sub 13}H{sub z} as a function of the Fe/Mn/Si ratio. Both the paramagnetic and ferromagnetic phases were observed as peak overlaps in the patterns around the Curie temperature (T{sub C}) occurring continuously in a temperature range of about 5 K around T{sub C.} Using the Williamson-Hall method, we evaluate the strain developing in the crystallites during the transition and find that it is associated with the growth of the paramagnetic phase as the transition occurs. Based on our measurements and microstructure analyses, we propose that cracking during the phase transition is due to or aggravated by the small content of a La-rich phase.},
doi = {10.1063/1.4960358},
journal = {Applied Physics Letters},
number = 5,
volume = 109,
place = {United States},
year = {Mon Aug 01 00:00:00 EDT 2016},
month = {Mon Aug 01 00:00:00 EDT 2016}
}
  • We investigate the temperature induced ferromagnetic to paramagnetic phase transition in Co substituted La(Fe{sub x}Co{sub y}Si{sub 1−x−y}){sub 13} with x = 0.9 and low Co content of y = 0.015 (T{sub c}≃200 K) by means of magneto-optical imaging with indicator film and by calorimetry at very low temperature rates. We were able to visualize the motion of the ferromagnetic (FM)/paramagnetic (PM) front which is forming reproducible patterns independently of the temperature rate. The average velocity of the FM/PM front was calculated to be 10{sup −4} m/s during the continuous propagation and 4×10{sup −3} m/s during an avalanche. The heat flux was measured at low temperature rates bymore » a differential scanning calorimeter and shows a reproducible sequence of individual and separated avalanches which occurs independently of the rate. We interpret the observed effects as the result of the athermal character of the phase transition.« less
  • The He I photoelectron spectra of ({eta}{sup 5}-C{sub 5}H{sub 4}CH{sub 3})Mn(CO){sub 2}HSiHPh{sub 2}, ({eta}{sup 5}-C{sub 5}H{sub 4}CH{sub 3})Mn(CO){sub 2}HSiPh{sub 3}, and ({eta}{sup 5}-C{sub 5}H{sub 4}CH{sub 3})Mn(CO){sub 2}HSiFPh{sub 2} (Ph = C{sub 6}H{sub 5}) have been obtained in order to measure the nature and extent of Si-H bond interaction with the transition-metal center in these complexes. The principal electronic structure factors contributing to the addition of the Si-H bond to the transition metal involve the interaction of the Si-H {sigma} and {sigma}* orbitals with the metal. The extent of Si-H {sigma}I interaction with the metal is obtained from the shape andmore » splitting pattern of the metal-based ionization band. The electron distribution between the Si-H bond and the metal is indicated by the relative stabilities of the metal-based and ligand-based ionizations. It is found that the metal-based ionizations of these complexes reflect the formal d{sup 6} electron count at the metal center. Also, the small shifts of the valence ionizations reveal that the extent of electron charge density shift from the metal to the ligand is negligible. These observations show that the electronic structure of the Si-H interaction with the metal is in the initial stages of Si-H bond addition to the metal, before oxidative addition has become prevalent.« less
  • The valence photoelectron spectra of ({eta}{sup 5}-C{sub 5}H{sub 4}CH{sub 3})Mn(CO)(L)HSiCl{sub 3} and ({eta}{sup 5}-C{sub 5}H{sub 4}CH{sub 3})Mn(CO)(L)HSiHPh{sub 2}, where L is CO or P(CH{sub 3}){sub 3}, are compared to determine the effect of ligand substitution at the metal center on Si-H bond activation. Metal centers that are more electron rich may promote more complete oxidative addition of the Si-H bond to the metal. The shifts in the metal and ligand ionization energies and the relative intensities of ionizations in the He I and He II photoelectron experiments show that the metal in ({eta}{sup 5}-C{sub 5}H{sub 4}CH{sub 3})Mn(CO)(PMe{sub 3})HSiCl{sub 3} ismore » best represented by a formal oxidation state of III (d{sub 4} electron count). This indicates nearly complete oxidative addition of the Si-H bond to the metal center and results in independent Mn-H and Mn-Si bonds. In contrast, the splitting and intensity pattern of the metal-based ionizations of ({eta}{sup 5}-C{sub 5}H{sub 4}CH{sub 3})Mn(CO)(PMe{sub 3})HSiHPh{sub 2} reflect the formal d{sup 6} electron count of a metal corresponding to oxidation state I. The extent of electron charge density shift from the metal to the ligand is also small, as evidenced by the negligible shifts of these ionizations from those of the related ({eta}{sup 5}-C{sub 5}H{sub 4}CH{sub 3})Mn(CO){sub 2}(PMe{sub 3}) complex. These observations indicate that the electronic structure of the Si-H interaction with the metal in this complex is in the initial stages of Si-H bond addition to the metal, before oxidative addition has become prevalent. 25 refs., 6 figs., 1 tab.« less
  • Two new layered silicates, La{sub 4}Mn{sub 5}Si{sub 4}O{sub 22} and La{sub 4}V{sub 5}Si{sub 4}O{sub 22}, have been prepared and their structures determined. La{sub 4}Mn{sub 5}Si{sub 4}O{sub 22} and La{sub 4}V{sub 5}Si{sub 4}O{sub 22} crystallize in the monoclinic space group C2/m: a = 14.024(2), b = 5.571(2), c = 11.703(2) {angstrom}, {beta} = 114.34(4){degrees} with Z = 2 formula units per cell and a = 13.510(3), b = 5.605(1), c = 11.114(2) {angstrom}, {beta} = 100.45(3){degrees} with Z = 2 formula units per cell, respectively. The structures were determined by single-crystal X-ray diffraction and refined to residuals of R = 2.73%more » and 3.82%, respectively. The manganese compound crystallizes in the perrierite structure while the vanadium compound crystallizes in the related chevkinite structure. Both perrierite and chevkinite display nearly eclipsed sorosilicate groups which separate rutile-like sheets of edge-shaped transition metal-oxygen octahedra from single, isolated transition metal-oxygen octahedra. Metal-metal distances within the rutile-like sheet are on the order of 2.8 {angstrom} in both compounds, approximately R{sub c}, the critical metal-metal distance defined by Goodenough for appreciable metal-metal interactions and electronic delocalization. Preliminary magnetic data are also presented. 28 refs., 9 figs., 3 tabs.« less