  Phase coexistence phenomena have been intensively studied in strongly
correlated materials where several ordered states simultaneously occur or
compete. Material properties critically depend on external parameters and
boundary conditions, where tiny changes result in qualitatively different
ground states. However, up to date, phase coexistence phenomena have
exclusively been reported for complex compounds composed of multiple elements.
Here we show that charge- and magnetically ordered states coexist in
double-layer Fe on Rh(001). Scanning tunneling microscopy and spectroscopy
measurements reveal periodic charge order stripes below a temperature of 130 K.
Close to liquid helium temperature, they are superimposed by ferromagnetic
domains as observed by spin-polarized scanning tunneling microscopy.
Temperature-dependent measurements reveal a pronounced cross-talk between
charge and spin order at the ferromagnetic ordering temperature about 70 K,
which is successfully modeled within an effective Landau theory including
sixth-order terms. Our results show that subtle balance between structural
modifications can lead to competing ordering phenomena.
