The McMaster University Nuclear Reactor (MNR) is a unique Canadian facility in a university environment welcoming researchers from across Canada and abroad. The irradiation and analytical facilities available cover a broad spectrum of nuclear analytical techniques from standard INAA to fully automated counting systems for prompt gamma activation analysis and delayed neutron counting. In addition, neutron beams provide for a wide spectrum of applied and basic nuclear research applications. This paper describes the state-of-the-art facilities available at McMaster.

The McMaster University Nuclear Reactor (MNR) research facilities

Crystal growth and properties of BaSn2Fe4O11

Intrinsic Auger signal profiles derived by Monte Carlo analysis

The strong, and heretofore unexplained, dependence of the magnetic properties of the R-type hexaferrites MX2Fe4O11 on heat treatment has been investigated by means of57Fe and119Sn Mossbauer spectroscopy at 297 K.57Fe Mossbauer spectra of samples of BaTi2Fe4O11, BaSn2Fe4O11, and SrSn2Fe4O11, annealed at several temperatures consist of three partially resolved quadrupole doublet patterns. The pattern with the very large quadrupole splitting, i.e. 1.3 mm s−1 ≤ δEQ ≤ 1.7 mm s−1, is readily assigned to the trigonal bipyramidal site, and exhibits no dependence of its parameters, including the relative intensity, on heat treatment. The remaining two patterns are assigned to Fe3+ ions on octahedral sites, and exhibit relative intensities that are strongly dependent on heat treatment. The119Sn spectrum of BaSn2Fe4O11 is a broad, apparently single line that, with the exception of verifying the presence of tin as Sn4+, provides little insight into the details of the structure. The distributions of the cations over all the lattice sites have been deduced from the Mossbauer spectra and compared with the magnetic susceptibility data. It is concluded that the cation distributions of the Sn-containing phase are not strongly dependent on heat treatment, and the magnetic properties exhibit a similar insensitivity to heat treatment. The Ti analogs exhibit a strong dependence of cation distribution on heat treatment, which is reflected in widely varying magnetic ordering temperatures, a variation that is confirmed by the incipient magnetic hyperfine splitting despite the strong magnetic frustration in the R-type hexaferrites.

/pdf/structure-property-relationships-in-the-r-type-hexaferrites-4o9ea50uid.pdf

Structure-property relationships in the R-type hexaferrites: Cation distributions and magnetic susceptibilities of MX 2 Fe 4 O 11

The broadening of the125Te Mossbauer spectral absorption with decreasing temperature in compounds of the type Cr2−xFexTexTeO6 (x=0.4, 0.8, 1.0, 1.5) is attributed to the presence of a supertransferred magnetic hyperfine field. The origin of the supertransferred magnetic hyperfine field, which is not observed in antiferromagnetically ordered Cr2TeO6 or Fe2TeO6, is associated with an imbalance in the magnetic exchange interaction at tellurium which results from the replacement of chromium by iron.

The supertransferred magnetic hyperfine field in chromium-iron tellurates.

A 57Fe and 119Sn Mössbauer study of BaFe4Sn2O11

The57Fe Mossbauer spectra recorded at 4.2K from the trirutile-type iron chromium tellurates of composition Fe2−xCrxTeO6, where x=0–2, show that the angle θ, which describes the perpendicular orientation of the magnetic moment to the basal plane of the Fe2TeO6 unit cell, is not changed by the incorporation of chromium until x exceeds 1.2 At this critical limit θ begins to rapidly cant to smaller values until, at compositions approaching Cr2TeO6, it approaches a parallel orientation to the basal plane. The125Te and129I Mossbauer spectra recorded from the compound FeCrTeO6 at 77 and 4.2K are consistent with the presence of a supertransferred magnetic hyperfine field at the tellurium nucleus ofca. 76 kG.

An investigation of iron chromium tellurates by iron-57, tellurium-125 and iodine-129 Mössbauer spectroscopy

Mossbauer data have been obtained from both the57Fe and119Sn isotopes for BaFe4Sn2O11. Variable temperature studies show that magnetic ordering occurs at ∼ 77K and is probably complete at 4K. Average hyperfine fields of 504kG and 45kG were observed at the iron and tin nuclei respectively.

C. Hallett

Papers

A 57Fe and 119Sn Mössbauer study of BaFe4Sn2O11

An investigation of iron chromium tellurates by iron-57, tellurium-125 and iodine-129 Mössbauer spectroscopy

Study of hexagonal R-type BaFe 4 Sn 2 O 11 by 57 Fe and 119 Sn Mössbauer spectroscopy