Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetoelastic coupling and Gr\"uneisen scaling in NdB$_4$   We report high-resolution capacitance dilatometry studies on the uniaxial
length changes in a NdB$_4$ single crystal. The evolution of magnetically
ordered phases below $T_{\rm N}$= 17.2~K (commensurate antiferromagnetic phase,
cAFM), $T_{\rm IT}$= 6.8~K (intermediate incommensurate phase, IT), and $T_{\rm
LT}$= 4.8~K (low-temperature phase, LT) is associated with pronounced anomalies
in the thermal expansion coefficients. The data imply significant
magneto-elastic coupling and evidence of a structural phase transition at
$T_{\rm LT}$ . While both cAFM and LT favor structural anisotropy $\delta$
between in-plane and out-of-plane length changes, it competes with the IT-type
of order, i.e., $\delta$ is suppressed in that phase. Notably, finite
anisotropy well above $T_{\rm N}$ indicates short-range correlations which are,
however, of neither cAFM, IT, nor LT-type. Gr\"uneisen analysis of the ratio of
thermal expansion coefficient and specific heat enables the derivation of
uniaxial as well as hydrostatic pressure dependencies. While $\alpha$/$c_{\rm
p}$ evidences a single dominant energy scale in LT, our data imply precursory
fluctuations of a competing phase in IT and cAFM, respectively. Our results
suggest the presence of orbital degrees of freedom competing with cAFM and
successive evolution of a magnetically and orbitally ordered ground state.

21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an