Spin Glass State in Strained La_2/3Ca_1/3MnO₃ Thin Films

Area of Science:

• Condensed Matter Physics
• Materials Science
• Thin Film Magnetism

Background:

• Epitaxial strain significantly alters thin film properties.
• Previous work identified a non-ferromagnetic layer (NFL) in La_2/3Ca_1/3MnO₃ thin films due to strain.
• The magnetic state of this strain-induced NFL remained uncharacterized.

Purpose of the Study:

• To comprehensively characterize the magnetic state of the strain-induced NFL in La_2/3Ca_1/3MnO₃ thin films.
• To determine if the NFL exhibits antiferromagnetic or other magnetic ordering.
• To understand the underlying magnetic interactions within the NFL.

Main Methods:

• Magnetic characterization including field-cooled magnetic hysteresis loops.
• Temperature-dependent analysis of exchange bias and coercive fields.
• Low-energy muon spectroscopy (LEMS) to probe magnetic dynamics.

Main Results:

• Exchange bias and coercive fields observed below 80 K, indicating interfacial magnetic effects.
• Exponential decay of these fields with temperature suggests spin-glass (SG) behavior.
• LEMS directly confirmed slowing down of magnetic moments below 100 K in the NFL.

Conclusions:

• The strain-induced NFL in La_2/3Ca_1/3MnO₃ exhibits spin-glass (SG) characteristics.
• The SG state arises from competing ferromagnetic and antiferromagnetic interactions of similar energy.
• This finding provides crucial insights into strain-mediated magnetism in thin films.