TY - JOUR

T1 - Order parameter of holmium in a magnetic field

AU - Tarvin, J. A.

AU - Eckert, J.

N1 - Funding Information:
THE ANTIFERROMAGNETIC to paramagnetic phase transition in MnO is first order \[11in the absence of an applied stress. However, a symmetry-breaking stress of 5 kbar along \[111\]causes the transition to pass through a tricritical point \[2\]and become second order. Bak et aL \[3\]have explained that this behavior occurs because the stress reduces the number of components (n) of the order parameter from eight to two. In like manner, one should be able to change the universality class of a second order phase transition by applying a symmetry-breaking field which reduces n. It was suggested \[4\]that an ideal candidate for a test of this hypothesis is the magnetic phase transition which occurs in Ho at TN = 131 K. Holmium has a hexagonal close-packed crystal structure\[5\]witha= 3.577A.At 131Kthemoments order in a helical \[5\]structure. They are perpendicular to the c-axis and are ferromagnetically aligned in the hexagonal basal planes. Moments in adjacent layers are canted with respect to one another by an angle ~ which varies from 50°at 131 K to 30°at 20K \[5\]A. t lower temperatures and in applied magnetic fields, there are several other phases \[6\]T. he 131 K transition, which is of second order, is the subject of this paper. In the helical phase there are four linearly independent structures, enumerated as follows: within a given basal plane, there are two independent directions (at right angles) in which the moments may align; and, for either orientation, the helix may be right-or left-handed. Since this is a three-dimensional system, it should be represented by an n = 4, d = 3 model \[7\]I.n a previous * Research supported by the Division of Basic Energy Sciences, Department of Energy, under Contract No. EY-76-C.02.0016.

PY - 1979/5

Y1 - 1979/5

N2 - The order parameter of the second order magnetic phase transition in Ho at 131 K has been measured in a magnetic field by neutron diffraction. It was expected that the applied field would change the number of components (n) of the order parameter from four to two. Such a change would be visible in the order parameter exponent β. However, in a field of 40 kOe, β is found to be 0.38 ± 0.02, in agreement with the zero field measurement and with an n = 4 model and in contradiction to an n = 2 model.

AB - The order parameter of the second order magnetic phase transition in Ho at 131 K has been measured in a magnetic field by neutron diffraction. It was expected that the applied field would change the number of components (n) of the order parameter from four to two. Such a change would be visible in the order parameter exponent β. However, in a field of 40 kOe, β is found to be 0.38 ± 0.02, in agreement with the zero field measurement and with an n = 4 model and in contradiction to an n = 2 model.

UR - http://www.scopus.com/inward/record.url?scp=0018470691&partnerID=8YFLogxK

U2 - 10.1016/0038-1098(79)90655-0

DO - 10.1016/0038-1098(79)90655-0

M3 - Article

AN - SCOPUS:0018470691

SN - 0038-1098

VL - 30

SP - 375

EP - 379

JO - Solid State Communications

JF - Solid State Communications

IS - 6

ER -