Odd spin frustration in ultrathin Cr(001) films studied by spin-polarized scanning tunneling microscopy

3-nm-thick Cr(001) films have been fabricated successfully with atomically flat and clean terraces. Images of both the topological and magnetic structures of the Cr films were obtained at 300 K using spin-polarized scanning tunneling microscopy. The observed magnetic image of the Cr(001) surface indicated that the topological antiferromagnetic (AF) order appeared in a series of adjacent terraces with two types of spin frustration caused by screw dislocations leading to the modification of the topological AF order. One type of the spin frustration is accompanied with the narrow domain wall between two screw dislocations. The other type is due to complex spin frustration caused by a cluster of odd number of screw dislocations, which is explained through a micromagnetic simulation.