Exploring thermally induced states in square artificial spin-ice arrays

Abstract

We present a methodology to explore experimentally the formation of thermally induced long-range ground-state ordering in artificial spin-ice systems. Our novel approach is based on the thermalization from a square artificial spin-ice array of elongated ferromagnetic nanoislands made of a FeNi alloy characterized by a Curie temperature about 100 K lower than that of Permalloy (Ni 81 Fe 19 ), which is commonly used for this kind of investigation. The decrease in M(T) when the sample is heated close to its Curie temperature reduces the shape anisotropy barrier of each island and allows us to bring the artificial spinice pattern above the blocking temperature of the islands, thus 'melting' the spin-ice system, without damaging the sample. The magnetization configuration resulting from the thermal excitation of the islands and the frustrated dipolar interactions among them can be then imaged by magnetic force microscopy or any other kind of magnetic microscopy imaging after cooling down the sample back to room temperature. This thermally induced melting-freezing protocol can be repeated as many times as desired on the same sample and the heating and cooling parameters (max T, heating and cooling rates, number of cycles, application of external fields) varied at will. Thereby, the approach proposed here opens up a pathway to the systematic experimental study of thermally induced frozen states in artificial spin-ice systems, which have been the subject of many recent theoretical studies due to their interesting physical properties but, because of the difficulties in obtaining them in real samples and in a controlled manner, remain experimentally an almost completely unexplored terrain.

Tunable nonequilibrium dynamics of field quenches in spin ice

“…With the advent of incipient thermal ensembles of artificial spin ice, where the constituent degrees of freedom can even be imaged individually in real space, there seems to be an entirely new setting for the study of these phenomena on the horizon (32)(33)(34)(35).…”

Emergent reduced dimensionality by vertex frustration in artificial spin ice

“…Simple square and kagome artificial spin ice lattices have been subject to intense study because they provide unique insight into the consequences of frustrated magnetism, such as residual entropy 9,10 and magnetic charge excitations [11][12][13][14] . In the last few years, improved thermalization methods have provided access to the low energy phases of artificial spin ice structures 10,15,16 and even their dynamics [17][18][19] . There is now growing awareness that one could even employ these artificial systems to design desired emergent behaviors and exotic states 20 .…”

FePd3as a material for studying thermally active artificial spin ice systems

“…More recently, a new experimental approach has been devised that seeks thermal activation in these physical simulators by heating close to the Curie temperature (T C ) of the constituent materials [17][18][19][20][21][22][23][24][25]. In this technique, the lithographically-patterned single-domain nanoscale bar magnets that comprise the structure may begin to exhibit spontaneous reversal, driven simultaneously by thermal effects and by the local magnetic environment.…”