Magnetic alignment in nominally non-magnetic hexagonal metal hydrides: NMR

Area of Science:

• Solid State Physics
• Materials Science
• Nuclear Magnetic Resonance (NMR)

Background:

• Hexagonal metal hydrides and deuterides are typically characterized using NMR spectroscopy.
• These materials exhibit very small magnetic susceptibilities, indicated by sharp NMR lines.
• The behavior of these materials in strong magnetic fields, particularly their alignment, is not well-understood.

Purpose of the Study:

• To investigate the unexpected magnetic field-induced alignment of hexagonal metal hydride and deuteride powders.
• To determine the extent and preferred direction of this alignment in specific materials.
• To measure magnetic susceptibilities and understand their role in the observed alignment.

Main Methods:

• Utilized strong magnetic fields (4.4-8.3 Tesla) for Nuclear Magnetic Resonance (NMR) experiments.
• Observed and quantified the alignment of powder crystallites within the magnetic field.
• Performed bulk magnetization measurements on aligned ZrBe2H1.4 powder to determine magnetic susceptibilities (χ∥ and χ⊥).

Main Results:

• Powders of ZrBe2(H,D)x, LuD3, and YD3 exhibit unexpected alignment in magnetic fields.
• Alignment extent ranges from nearly complete in ZrBe2(H,D)x to barely detectable in YD3.
• ZrBe2(H,D)x aligns with its c-axis perpendicular to the field, while LuD3 and YD3 align with the c-axis parallel to the field.

Conclusions:

• Magnetic field-induced alignment is a significant phenomenon in these hexagonal metal hydrides/deuterides, despite low bulk susceptibility.
• The crystallographic orientation relative to the magnetic field differs between the studied systems.
• This alignment must be accounted for when interpreting NMR spectra of these and similar materials.