Mission Statement

Scientists are interested in studying magnetic materials because the exotic behavior exhibited in these materials is important for both fundamental research and device technology. The determination of magnetic structures and the evolution of magnetic correlations are key features for understanding the intrinsic properties of magnetic materials.

The high-flux, low-background, and exceptionally clean beam offered by the Fixed-Incident-Energy Triple-Axis (FIE-TAX) Spectrometer allows researchers to study the magnetic and structural phase transitions in single crystals and thin films as a function of temperature, magnetic field, and pressure. Researchers also use HB-1A for studying low-lying magnetic excitations and high-temperature phonons.

Instrument Description

The 14.6 meV HB-1A FIE-TAX spectrometer uses a double pyrolytic graphite monochromator system. The first monochromator unit is vertically focused, and the second unit can either be vertically or doubly focused. Two highly oriented pyrolytic graphite filters, one after each monochromator, are used to reduce λ/2 contamination. The filters, together with the double monochromator system, provide HB-1A with an exceptionally clean beam in terms of higher-order contamination neutrons: Iλ/2 ≈ 10-4 × Iλ. This spectrometer also has one of the most intense beams at this energy at HFIR, as well as a very low γ and fast neutron background. Typical energy resolution is ~1 meV, but the energy resolution width can be reduced to ~0.5 meV using the beryllium analyzer. Due to the high-flux, low-background, and very low higher-order contaminations of the beam, HB-1A is one of the few instruments that can measure weak magnetic scattering of tiny single crystals (m > 2 mg) and thin film samples with various sample environments, including studies requiring ultra-low temperatures (T > 40 mK), applied magnetic fields (H < 8 T), and applied pressures (P < 2GPa).


  • Elastic studies of single crystals and thin films, to determine crystallographic and magnetic structures, transitions, and phase diagrams under various conditions (T, H, P)
  • Studies of low-lying magnetic excitations up to ~ 9 meV using neutron energy loss and high-temperature phonons up to ~35 meV using neutron energy gain


Beam Spectrum:Thermal
Monochromator:PG(002) double crystal
Monochromator angle:2Θ M = 41.3° Ei = 14.64 meV
Analyzers:PG(002) Be(101) Be(002) Si(111)
Sample angles:0° < Ψ < 360°
Scattering angle:-5 to 135°
Analyzer angles:-60° < 2ΘA < 120°
Collimations (FWHM):Premonochromator: 40′
Monochromator-sample: 20′, 40′
Sample-analyzer: 20′, 40′, 60′, 80′ 
Analyzer-detector: 20′, 40′, 60′, 80′, 140′, 240′
Beam Size:40 × 150 mm max
Filters:Sapphire pre-Monochromator
2 HOPG (λ / 2 ≈ 10-4λ) located between
M-1 and M-2 and after M-2
Flux at sample:~2 × 107 n/cm2/s