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# Takeshi Egami <egami@utk.edu>
# requesting 6 days, at minimum=5 days
# beamline 33ID, Structure of Superconducting Watery Cobaltate
# instrument 33ID-D kappa
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# top:/home/www/beamtime-requests/req00555.txt
# UNICAT Member Beam Time Request  #555
# created Wed Mar 17 09:28:29 CST 2004
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beamline:
	33ID

collaboration:
	Yes

collaborator_Hawoong:
	ON

collaborator_Paul:
	ON

collaborator_Pete:
	ON

contact:
	egami@utk.edu

days:
	6

description:
	Summary:

	High-energy powder diffraction and medium energy single crystal diffraction will be carried out on Na0.3CoO2•1.4H2O.  The measurement will complement the neutron scattering results to clarify the detailed structure of this newly discovered superconductor.


Motivation:

	Na0.3CoO2•1.4H2O is the newest family of transition metal oxide superconductor.  While its critical temperature is low (TC = 4.5 K), cobaltates are closer to the cuprates than other any oxides examined recently, such as ruthenates.  But what is most conspicuous is the presence of water.  The mother compound is NaCoO2, and reduction of Na dopes holes into the CoO2 layers.  The conventional thinking is that H2O provides separation between the CoO2 layers.  Recently we carried out pulsed neutron atomic pair-density function (PDF) analysis on the deutrated compound, and found strong evidence that water is not only separating the CoO2 layers and making the solid more two-dimensional, but actually playing a more active role.  Our results suggest that the water molecules are strongly modified from the usual structure.  While the O-D distance is normal (0.96 Ĺ), the D-D distance is widely distributed from 1.5 to 1.8 Ĺ (the standard distance in the molecule is 1.6 Ĺ).  This result is consistent with the presence of doped on the oxygen of D2O, and suggests that water may be “metallic”.  This is a big discovery.

Proposed Experiment:

Experiment:
	
	Dave Mandrus and Brian Sales have succeeded in growing a single crystal of this compound.  We will study the diffraction at 12 keV and at the Co K-edge to determine
1.	Na short-range ordering suspected by the powder measurement.
2.	Diffuse scattering due to local displacement, for instance those of oxygen 
reflecting the Jahn-Teller distortion.  This measurement has to be done at low 
temperatures.
During the last cycle we have confirmed the presence of superlattice peaks that correspond to Na ordering.  Princeton group, however, claim that they have seen the evidence of charge ordering in the cobalt layer in the system without water.  I am not convinced of that, but we will look for such evidence for the superconducting sample.  This measurement will require 6 days.

equipment_required:
	displex, Ge detector

experiment:
	Structure of Superconducting Watery Cobaltate

foreign_nationals:
	Cinzia Metallo, Ferenc Stercel

hazards:
	None.

instrument:
	33ID-D kappa

instrument_other:
	

minimumdays:
	5

name:
	Takeshi Egami

nonmembers:
	

unacceptable_dates:
	

z34ID_details:
	


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