  As an alternative angular momentum carrier, magnons or spin waves can be
utilized to encode information and breed magnon-based circuits with ultralow
power consumption and non-Boolean data processing capability. In order to
construct such a circuit, it is indispensable to design some electronic
components with both long magnon decay and coherence length and effective
control over magnon transport. Here we show that an all-insulating magnon
junctions composed by a magnetic insulator (MI1)/antiferromagnetic insulator
(AFI)/magnetic insulator (MI2) sandwich (Y3Fe5O12/NiO/Y3Fe5O12) can completely
turn a thermogradient-induced magnon current on or off as the two Y3Fe5O12
layers are aligned parallel or anti-parallel. The magnon decay length in NiO is
about 3.5~4.5 nm between 100 K and 200 K for thermally activated magnons. The
insulating magnon valve (magnon junction), as a basic building block, possibly
shed light on the naissance of efficient magnon-based circuits, including
non-Boolean logic, memory, diode, transistors, magnon waveguide and switches
with sizable on-off ratios.
