  Ground state and low-energy excitations of the quasi-one-dimensional
antiferromagnet CuSe$_2$O$_5$ were experimentally studied using bulk
magnetization, neutron diffraction, muon spin relaxation and antiferromagnetic
resonance measurements. Finite interchain interactions promote long-range
antiferromagnetic order below $T_N=17$ K. The derived spin canted structure is
characterized by the magnetic propagation vector $\mathbf{k}=(1, 0, 0)$ and the
reduced magnetic moment $\bm{m}=[0.13(7), 0.50(1), 0.00(8)]\mu_B$. The values
of the magnetic anisotropies determined from the field and angular dependencies
of the antiferromagnetic resonance comply well with a previous electron
paramagnetic resonance study and correctly account for the observed magnetic
ground state and spin-flop transition.
